,,lessons ,,on ,,soil ,,by ,e4 ,j4 ,,russell1 ,d4,sc4 7,lond47 ,,goldsmith ,,company',s ,,soil ,,chemist1 ,,rothamsted ,,experimental ,,station ,cambridge3 at the ,university ,press #aiaa ,transcriber's note3 ,page numbers in this book are indicated by numbers enclosed in curly braces1 e4g4 #ii4 ,they have been located where page breaks occurred in the original book1 in accordance with ,project ,gutenberg's ,,faq-,v-#ii4 ,in the ,,html version of this book1 page numbers are placed in the left margin4 v ,,preface ,the ,syndics of the ,cambridge ,university ,press propose to issue a ,nature ,study ,series of which this is the first volume4 ,we count ourselves fortunate in securing ,dr ,e4 ,j4 ,russell as author and ,soil as subject4 ,the subject is fundamental1 for1 just as the soil lies beneath the plant and animal life we see1 so is a knowledge of the soil necessary for all understanding of flora and fauna4 ,the real complexity of the apparently simple element ,earth1 and the variety of methods required for exploring it1 are typical of the problems which the tout ensemble of the outdoor world presents to the naturalist4 ,dr ,e4 ,j4 ,russell has not only acquired a first-rate and first-hand knowledge of his subject at ,wye and at ,rothamsted2 his own researches have recently extended our knowledge of the micro-organisms in the soil and their influence on fertility4 ,further1 what is very much to our purpose1 he has himself had practical experience in teaching at an elementary school in ,wye and at a secondary school in ,harpenden4 ,just at the present moment1 ,county ,councils are trying to push rural education and to awaken the intelligence of country children by interesting them in their surroundings4 ,it is1 therefore1 a favourable opportunity to offer these pages as a concrete suggestion in model lessons and object lessons1 showing exactly what can be done under existing conditions4 vi ,the book is intended to help children to study nature2 there is no attempt to substitute book study for nature study4 ,hence1 whilst there are passages of continuous reading1 it is not a mere reader4 ,many teachers1 myself among them1 have felt the difficulty of organising practical work for large classes4 ,dr ,russell has written so that1 whilst nominally showing the pupil how to learn1 he is secretly scattering hints for the teacher who is learning how to teach4 ,abundant and varied practical exercises have been suggested1 and careful instructions have been given so that the book shall seem intelligible even in the absence of a teacher4 ,the proposed practical work is not only what might be done by eager boys and girls on half-holidays1 but what can be done by every scholar in the course of ordinary school work4 ,the pictorial illustrations are intended as aids to observation1 not as substitutes4 ,drawing is one form of practical exercise1 and the preparation of corresponding illustrations in the scholars' notebooks from the apparatus used in the classroom and the fields around the school may afford exercises in artistic work with pen1 brush or camera4 ,sufficient directions are given for the supply of necessary materials and apparatus4 ,the apparatus proposed is of the simplest character4 ,it is suggested that the book will be found most useful in the higher standards of elementary schools1 in preparatory schools and in the lower forms of secondary schools1 that is1 where the ages of scholars average from #ab to #ad4 ,,hugh ,,richardson ,,york1 #g ,january #aiaa vi ,,contents ,,chap4 ,,page ,i4 ,,what ,,is ,,the ,,soil ,,made ,,of8 4 4 4 4 4 4 4 4 4 4 4 4 4 #a ,,ii4 ,,more ,,about ,,the ,,clay 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #i ,,iii4 ,,what ,,lime ,,does ,,to ,,clay 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ai ,,iv4 ,,some ,,experiments ,,with ,,the ,,sand 4 4 4 4 4 4 4 4 4 4 4 #bb ,v4 ,,the ,,part ,,that ,,burns ,,away 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #cc ,,vi4 ,,the ,,plant ,,food ,,in ,,the ,,soil 4 4 4 4 4 4 4 4 4 4 4 4 4 #da ,,vii4 ,,the ,,dwellers ,,in ,,the ,,soil 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ec ,,viii4 ,,the ,,soil ,,and ,,the ,,plant 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #fd ,,ix4 ,,cultivation ,,and ,,tillage 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #hb ,x4 ,,the ,,soil ,,and ,,the ,,countryside 4 4 4 4 4 4 4 4 4 4 4 4 #ajj ,,xi4 ,,how ,,soil ,,has ,,been ,,made 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #aaf ,,appendix 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #abh ,,index 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #acb ,transcriber's note3 ,the page numbers below are those in the original book4 ,however1 in this e-book1 to avoid the splitting of paragraphs1 the illustrations may have been moved to the page preceding or following4 ,,list ,,of ,,illustrations ,,figure ,,page #a4 ,soil and subsoil in ,st ,george's ,school garden 4 4 4 4 #b #b4 ,columns showing what #ajj parts of soil and subsoil were made of 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #d #c4 ,columns showing what #ajj parts of dried soil and subsoil were made of 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #h #d4 ,clay shrinks when it dries 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #aa #e4 ,clay swells up when it is placed in water 4 4 4 4 4 4 #ab #f4 ,landslip in the ,isle of ,wight4 ,phot4 ,valentine ,son 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ac #g4 ,clay does not let water run through 4 4 4 4 4 4 4 4 4 #ad #h4 ,sand allows air to pass through but clay does not 4 4 #ae #i4 ,a brick allows both air and water to pass through it #ag #aj4 ,lime added to turbid clay water soon makes the clay settle 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #bj #aa4 ,sand dunes1 ,penhale1 ,cornwall4 ,phot4 ,geological ,survey 4 4 4 4 4 4 4 4 4 4 4 4 4 #bc #ab4 ,blowing sand covering up meadows and ruining them4 ,phot4 ,geological ,survey 4 4 4 4 4 4 4 4 4 4 4 4 4 #be #ac4 ,model of a spring 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #bf #ad4 ,foot of chalk hill at ,harpenden where a spring breaks out4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 4 4 4 4 #bg #ae4 ,the little pool and the spring4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #bh #af4 ,water spouting up from a bore hole1 ,old ,cateriag ,quarry1 ,dunbar4 ,phot4 ,geological ,survey 4 4 4 4 4 #bi #ag4 ,sandy soils in wet and in dry positions 4 4 4 4 4 4 4 #ca #ah4 ,map of the roads round ,wye 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #cb #ai4 ,peat bog in ,hoy1 ,orkney3 peat is being cut for fuel4 ,phot4 ,valentine ,son 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ci #bj4 ,rye growing in surface soil1 subsoil1 and sand 4 4 4 4 #db #ba4 ,mustard growing in surface soil1 subsoil1 and sand 4 4 #dc #bb4 ,mustard growing in soil previously cropped with rye1 and in soil previously uncropped 4 4 4 4 4 4 4 4 4 4 #de #bc4 ,pieces of grass1 leaves1 etc4 change to plant food in the surface soil lint not in the subsoil 4 4 4 4 4 #ej #bd4 ,soil in which earthworms have been living and making burrows 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ee #be4 ,fresh soil turns milk bad1 but baked soil does not 4 4 #eg #bf4 ,soil contains tiny living things that grow on gelatine #eh #bg4 ,our breath makes lime water turn milky 4 4 4 4 4 4 4 4 #ei #bh4 ,something in the soil uses up air and makes lime water turn milky 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #fa #bi4 ,soils are able to stick to water3 clay or loam soils do this better than sands 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #fe #cj4 ,water can pass from wet to dry places in the soil1 it can even travel upwards 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ff #ca4 ,plants growing in soils supplied from below with water4 ,all the water the plants get has to travel upwards #fg #cb4 ,mustard growing in soils supplied with varying quantities of water 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #fi #cc4 ,wheat growing in moist and in dry soils 4 4 4 4 4 4 4 #ga #cd a and b4 ,plants found on a dry soil had narrow leaves1 those on a moist soil had wider leaves4 ,phot4 ,s4 ,t4 ,parkinson 4 4 4 4 4 4 4 4 4 #gb1 #gc #ce4 ,plants give out water through their leaves 4 4 4 4 4 4 #gd #cf4 ,stephen ,hales's experiment in #agbg 4 4 4 4 4 4 4 4 4 4 #ge #cg4 ,hill slope near ,harpenden showing woodland at top and arable land lower down4 ,phot4 ,lionel ,armstrong #gg #ch4 ,view further along the valley2 woodland and arable above1 rough grassland near the river4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #gi #ci4 ,rough grass pasture near the river4 ,higher up is arable land4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 #ha #dj4 ,after harvest the farmer breaks up his land with a plough and then leaves it alone until seed time4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #hc #da4 ,rolling in mangold seed on the farm4 ,phot4 ,h4 ,b4 ,hutchinson 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #he #db4 ,soil sampler 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #hh #dc4 ,cultivation and mulching reduce the loss of water from soils 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ij #dd a and b4 ,maize cannot compete successfully with weeds 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #id1 #ie #de4 ,a plot of wheat left untouched since #ahhb at ,rothamsted has now become a dense thicket4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #ig #df4 ,a badly drained wheat field 4 4 4 4 4 4 4 4 4 4 4 4 4 #ii #dg4 ,highly cultivated sandy soil in ,kent 4 4 4 4 4 4 4 4 4 #ajc #dh4 ,a ,surrey heath 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #aje #di4 ,woodland and heather on high sandy land1 ,wimbledon ,common4 ,phot4 ,r4 ,h4 ,carter 4 4 4 4 4 4 4 4 4 4 4 #ajg #ej4 ,poor sandy soil in ,surrey1 partly cultivated but mainly wood and waste 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #aji #ea4 ,open chalk cultivated country1 ,thanet 4 4 4 4 4 4 4 4 #aac #eb4 ,cliffs at the seaside1 ,manorbier4 ,phot4 ,geological ,survey 4 4 4 4 4 4 4 4 4 4 4 4 4 #aag #ec4 ,cliffs in inland district1 ,arthur's ,seat1 ,edinburgh4 ,phot4 ,geological ,survey 4 4 4 4 4 4 4 4 4 4 4 4 4 #aai #ed4 ,model of a stream 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #abj #ee4 ,the bend of a river 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #aba #ef4 ,the winding river--the ,stour at ,wye4 ,phot4 ,r4 ,h4 ,carter 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #abc #eg4 ,sketch map showing why ,godmersham and ,wye arose where they did on the ,stour 4 4 4 4 4 4 4 4 4 4 4 4 #abf #eh4 ,ford at ,coldharbour near ,harpenden4 ,phot4 ,lionel ,armstrong 4 4 4 4 4 4 4 4 4 4 4 4 4 4 #abg ,the photographs of the pot experiments are by ,mr ,lionel ,armstrong4 xi ,,introduction ,the following pages contain the substance of lessons given at the village school at ,wye to the #dth1 #eth1 #fth and #gth standards 7mixed7 and at ,st ,george's ,school1 ,harpenden1 to the #crd form4 ,there is1 however1 an important difference between the actual lessons and the book4 ,the lessons had reference to the soils round about the village1 and dealt mainly with local phenomena1 general conclusions being only sparingly drawn2 while in the book it has been necessary to throw the course into a more generalised form4 ,the teacher in using the book will have to reverse the process1 he must find local illustrations and make liberal use of them during the course2 it is hoped that the information given will help him over any difficulties he may experience4 ,this necessity for finding local illustrations constitutes one of the fundamental differences between ,nature ,study subjects and other subjects of the school curriculum4 ,the textbooks in some of the others may be necessary and sufficient2 in ,nature ,study it is at most only subsidiary1 serving simply as a guide to the thing that is to be studied2 unless the thing itself be before the class it is no better than a guide to a cathedral would be without the cathedral4 ,and just as the guide is successful only when he directs the attention of the stranger to the important features of the place1 and fails directly he becomes garrulous and distracts attention1 so a ,nature ,study book succeeds xii only in as far as it helps in the study of the actual thing1 and fails if it is used passively and is substituted for an active study4 ,no description or illustration can take the place of direct observation2 the simplest thing in ,nature is infinitely more wonderful than our best word pictures can ever paint it4 ,the author recommends the teacher to look through the chapter before it has to be taken in class and then to make a few expeditions in search of local illustrations4 ,it is not strictly necessary that the chapters should be taken in the order given4 ,the local phenomena must be dealt with as they arise and as weather permits1 or the opportunity may pass not to return again during the course4 ,in almost any lane1 field1 or garden a sufficient number of illustrations may be obtained for our purpose2 if a stream and a hill are accessible the material is practically complete1 especially if the children can be induced to pursue their studies during their summer holiday rambles4 ,of course this entails a good deal of work for the teacher1 but the results are worth it4 ,children enjoy experimental and observation lessons in which they take an active part and are not merely passive learners4 ,the value of such lessons in developing their latent powers and in stimulating them to seek for knowledge in the great book of ,nature is a sufficient recompense to the enthusiastic teacher for the extra trouble involved4 ,it is not desirable to work through a chapter in one lesson4 ,children unaccustomed to make experiments or to see experiments done1 will probably require three or four lessons for getting through each of the first few chapters1 and two or three lessons for each of the others4 xiii ,the pot experiments of ,chaps4 ,,vi41 ,,vii4 and ,,viii4 should be started as early in the course as possible4 ,twenty flower pots are wanted for the set2 they should be of the same size1 about eight inches being a convenient diameter1 and should be kept together in a warm place4 ,three are filled with sand1 seven with subsoil1 and the remaining ten with surface soil4 ,three of the subsoil pots are uncropped1 two being stored moist and one dry4 ,four pots of the surface soil are uncropped and moist1 a fifth and sixth are uncropped and dry1 one of these contains earthworms 7p4 #ed74 ,four glazed pots1 e4g4 large jam or marmalade jars1 are also wanted 7p4 #fi74 ,mustard1 buckwheat1 or rye make good crops1 but many others will do4 ,leguminous crops1 however1 show certain abnormal characters1 while turnips and cabbages are apt to fail3 none of these should be used4 ,it is highly desirable that the pots should be duplicated4 ,the plots also should be started in the school garden as early as convenient4 ,eight are required for the set3 their treatment is described in ,chap4 ,,ix4 ,plots two yards square suffice4 ,a supply of sand1 of clay1 and of lime will be wanted1 but it is not necessary to have fresh material for each lesson4 ,the sand may be obtained from a builder1 a sand pit1 the sea shore or from a dealer in chemical apparatus4 ,the clay may be obtained from a brick yard2 it gives most satisfactory results after it has been ground ready for brick making4 ,modelling clay is equally satisfactory4 ,a supply of rain water is desirable4 ,for a class of twelve children working in pairs at the experiments the following apparatus is wanted for the whole course3-- xiv ,six tripods and bunsen burners or spirit lamps #b twelve pipe-clay triangles #d twelve crucibles or tin lids #c sixteen gas jars #d twelve beakers #bej c4c4 capacity #d two beakers #ejj c4c4 two beakers #ajj c4c4 six egg-cups #b twelve funnels #c six funnel stands #a six perforated glass disks #c two tubulated bottles #ejj c4c41 four corks to fit cork borers #d lbs4 assorted glass tubing pestle and mortar twelve ,erlenmeyer flasks #ej c4c4 #c six saucers twelve flatbottomed flasks #ajj c4c41 six fitted with ,india rubber stoppers bored with one hole #c1 and six with ordinary corks #c box as in ,fig4 #ac six glass tubes #a_/b diameter1 #ah long #b six lamp chimneys #c six test tubes1 corks to fit three thermometers soil sampler 7p4 #hh7 balance and weights two retort stands with rings and clamp4 ,the figures given in square brackets are the quantities that suffice when the teacher alone does the experiments1 it not being convenient for the scholars to do much4 xv ,in conclusion the author desires to tender his best thanks to the ,rev4 ,cecil ,grant of ,st ,george's ,school1 and to ,mr ,w4 ,j4 ,ashby of the ,wye ,school1 for having allowed him the use of their schools and appliances during the progress of these lessons4 ,especially are his thanks due to ,mr ,lionel ,armstrong for much help ungrudgingly rendered in collecting material1 taking photographs1 and supervising the experiments4 ,e4 ,j4 ,r4 ,,harpenden1 ,february1 #aiaa4 #a ,,chapter ,i ,,what ,,is ,,the ,,soil ,,made ,,of8 ,apparatus required4 ,soil and subsoil from a hole dug in the garden4 ,clay4 ,six tripods and bunsen burners or spirit lamps #b4 ,six crucibles or tin lids and pipe-clay triangles #b4 ,twelve glass jars or gas cylinders #d4 ,six beakers #b #a4 ,if we talk to a farmer or a gardener about soils he will say that there are several kinds of soil2 clay soils1 gravel soils1 peat soils1 chalk soils1 and so on1 and we may discover this for ourselves if we make some rambles in the country and take careful notice of the ground about us1 particularly if we can leave the road and walk on the footpaths across the fields4 ,when we find the ground very hard in dry weather and very sticky in wet weather we may be sure we are on a clay soil1 and may expect to find brick yards or tile works somewhere near1 where the clay is used4 ,if the soil is loose1 drying quickly after rain1 and if it can be scattered about by the hand like sand on the sea shore1 we know we are on a sandy soil and can look for pits where builder's sand is dug4 ,but it may very likely happen that the soil is something in between1 and that neither sand pits nor #b clay pits can be found2 if we ask what sort of soil this is we are told it is a loam4 ,a gravel soil will be known at once by its gravel pits1 and a chalk soil by the white chalk quarries and old lime kilns1 while a peat soil is black1 sometimes marshy and nearly always spongey to tread on4 ,illustration3 ,fig4 #a4 ,soil and subsoil in ,st ,george's school garden ,we want to learn something of the soil round about us1 and we will begin by digging a hole about three feet deep to see what we can discover4 ,at ,harpenden this is what the scholars saw3--the top eight inches of soil was dark in colour and easy to dig2 the soil below was reddish brown in colour and very hard to dig2 one changed into the other so quickly that it was easy to see where the top soil ended and the bottom soil began2 no further change could1 however1 be seen below the eight inch line4 ,a drawing was made to show these things1 and is given in ,fig4 #a4 ,you may find something quite different3 sand1 chalk1 or solid rock may occur below the soil1 but you should enter whatever you see into your notebooks and make a drawing1 like ,fig4 #a1 to be kept for future use4 ,before filling in the hole some of the dark coloured top soil1 and some of the lighter coloured soil lying below 7which is called the subsoil71 #c should be taken for further examination2 the two samples should be kept separate and not mixed4 ,first look carefully at the top soil and rub some of it between your fingers4 ,we found that our sample was wet and therefore contained water2 it was very sticky like clay and therefore contained clay2 there were a few stones and some grit present and also some tiny pieces of dead plants--roots1 stems or leaves1 but some so decayed that we could not quite tell what they were4 ,a few pieces of a soft white stone were found that marked on the blackboard like chalk4 ,lastly1 there were a few fragments of coal and cinders1 but as these were not a real part of the soil we supposed they had got in by accident4 ,the subsoil was also wet and even more sticky than the top soil1 it contained stones and grit1 but seemed almost free from plant remains and from the white chalky fragments4 ,a few experiments will show how much of some of these things are present4 ,the amount of water may be discovered by weighing out ten grams of soil1 leaving it to dry in a warm place near the fire or in the sun1 and then weighing it again4 ,in one experiment the results were3-- ,weight of top soil before drying 444 #aj grams #ajj decigrams after 444 #h4c #hc ---- --- ,water lost 444 #a4g #ag ,a column #ajj millimetres long was drawn to represent the #ajj decigrams of soil1 and a mark was drawn #ag millimetres up to show the amount of water 7see ,fig4 #b74 ,weight of bottom soil before drying 444 #aj grams #ajj decigrams after 444 #h4g #hg ,water lost 444 #a4c #ac #d ,another column should be drawn for the subsoil4 ,on drying the soil it becomes lighter in colour and loses its stickiness1 but it has not permanently changed because as soon as water is added it comes back to what it was before4 ,illustration3 ,fig4 #b4 ,columns showing what #ajj parts of soil and subsoil were made of ,the dried lumps of soil are now to be broken up finely with a piece of wood1 but nothing must be lost4 ,it is easy to see shrivelled pieces of plant1 but not easy to pick them out2 the simplest plan is to burn them away4 ,the soil must be carefully tipped on to a tin lid1 or into a crucible1 heated over a flame and stirred #e with a long clean nail4 ,first of all it chars1 then there is a little sparkling1 but not much1 finally the soil turns red and does not change any further no matter how much it is heated4 ,the shade of red will at once be recognised as brick red or terra cotta1 indeed terra cotta means baked earth4 ,when the soil is cold it should be examined again2 it has become very hard and the plant remains have either disappeared or have changed to ash and crumble away directly they are touched4 ,on weighing a further loss is discovered1 which was in our experiment3-- ,weight of top soil after drying but before burning 444 #hc decigrams after 444 #gf -- ,the part that burnt away weighed 444 #g ,weight of subsoil after drying but before burning 444 #hg decigrams after 444 #hd -- ,the part that burnt away weighed 444 #c ,these results are entered on the column in ,fig4 #b4 ,the surface soil is seen to contain more material that will burn away than the subsoil does4 ,when the burnt soil is moistened it does not become dark and sticky like it did before1 it has completely changed and cannot be made into soil again4 ,it is more like brick dust than soil4 ,for further experiments we shall want a fresh portion of the original soil4 ,on a wet afternoon something was noticed that enabled us to get a little further with our studies4 ,the rain water ran down a sloping piece of ground in a tiny channel it had made2 the streamlet was very muddy1 and at first it was thought that all the soil was washed away4 ,but we soon saw that the channel was lined #f with grit1 some of which was moving slowly down and some not at all4 ,grit can therefore be separated from the rest of the soil by water4 ,this separation can be shown very well by the following experiment4 ,rub ten grains of finely powdered soil with a little water 7rain water is better than tap water71 and carefully pour the muddy liquid into a large glass jar4 ,add more water to the rest of the soil1 shake1 and again pour the liquid into the jar2 go on doing this till the jar is full4 ,then get some more jars and still keep on till the liquid is no longer muddy but nearly clear4 ,the part of the soil that remains behind and will not float over into the jars is at once seen to be made up of small stones1 grit1 and sand4 ,set the jars aside and look at them after a day or so4 ,the liquid remains muddy for some time1 but then it clears and a thick black sediment gathers at the bottom4 ,if now you very carefully pour the liquid off you can collect the sediments3 they are soft and sticky1 and can be moulded into patterns like clay4 ,in order to see if they really contain clay we must do the experiment again1 but use pure clay from a brick yard1 or modelling clay1 instead of soil4 ,the muddy liquid is obtained as before1 it takes a long time to settle1 but in the end it gives a sediment so much like that from the soil1 except in colour1 that we shall be safe in saying that the sediments in the jars contain the clay from the soil4 ,and thus we have been able to separate the sticky part of the soil--the clay--from the gritty or sandy part which is not at all sticky4 ,we may even be able to find out something more4 ,if we leave the soil sediment and the clay sediment on separate tin lids to dry1 and then examine them carefully we may find that the #g soil sediment is really a little more gritty than the clay4 ,although it contains the clay it also contains something else4 ,when the experiment is made very carefully in a proper way this material can be separated from the pure clay4 ,it is called silt1 but really there are a number of silts1 some almost like clay and some almost like sand2 they shade one into the other4 ,if there is enough grit it should be weighed3 we obtained #ad decigrams of grit from #aj grams of our top soil and #ag decigrams from #aj grams of bottom soil4 ,we cannot separate the clay from the silt1 but when this is done in careful experiments it is found that the subsoil contains more clay than the top soil4 ,we should of course expect this because we have found that the subsoil is more sticky than the top soil4 ,these results are put into the columns as before so that we can now see at once how much of our soil is water1 how much can burn away1 how much is grit1 and how much is clay and other things4 ,what would have happened if the sample had been dug out during wetter or drier weather8 ,the quantity of water would have been different1 but in other respects the soil would have remained the same4 ,it is therefore best to avoid the changes in the amount of water by working always with #aj grams of dried soil4 ,the results we obtained were3-- ,top soil ,subsoil ,weight of dry soil before burning 444 #ajj #ajj decigrams after 444 #ib #ig --- --- ,the part that burned away weighed 444 #h #c ,weight of grit from #aj grams of dried soil #ag #ai ,the columns are given in ,fig4 #c4 #h ,illustration3 ,fig4 #c4 ,columns showing what #ajj parts of dried soil and subsoil were made of ,summary4 ,the experiments made so far have taught us these facts3-- #a4 ,soil contains water1 grit or sand1 silt1 clay1 a part that burns away1 and some white chalky specks4 #b4 ,the top layer of soil to a depth of about eight inches is different from the soil lying below1 which is called the subsoil4 ,it is less sticky1 easier to dig1 and darker in colour4 ,it contains more of the material that burns away1 but less clay than the subsoil4 #c4 ,when soil is dried it is not sticky but hard or crumbly2 as soon as it is moistened it changes back to what it was before4 ,but when soil is burnt it completely alters and can no longer be changed back again4 #a ,see p4 xiv for explanation of the figures in square brackets4 #i ,,chapter ,,ii ,,more ,,about ,,the ,,clay ,apparatus required4 ,clay1 about #f lbs42 a little dried1 powdered clay2 sand1 about #f lbs4 ,six glass jars or cylinders #b4 ,six beakers #a4 ,six egg-cups #a4 ,six funnels and stands #b4 ,six perforated glass or tin disks #b4 ,six glass tubes #b4 ,two tubulated bottles fitted with corks4 ,some seeds4 ,six small jars about #b in4 x #a in4 #b4 ,bricks4 ,the apparatus in ,fig4 #i4 ,pestle and mortar4 ,we have seen in the last chapter that clay will float in water and only slowly settles down4 ,is this because clay is lighter than water8 ,probably not1 because a lump of clay seems very heavy4 ,further1 if we put a small ball of clay into water it at once sinks to the bottom4 ,only when we rub the clay between our fingers or work it with a stick--in other words1 when we break the ball into very tiny pieces--can we get it to float again4 ,we therefore conclude that the clay floated in our jars 7p4 #f7 for so long not because it was lighter than water1 but because the pieces were so small4 ,clay is exceedingly useful because of its stickiness4 ,dig up some clay1 if there is any in your garden1 or procure some from a brick works4 ,you can mould it into any shape you like1 and the purer the clay the #aj better it acts4 ,enormous quantities of clay are used for making bricks4 ,make some model bricks about an inch long and half an inch in width and depth1 also make a small basin of about the same size1 then set them aside for a week in a warm1 dry place4 ,they still keep their shape2 even if a crack has appeared the pieces stick together and do not crumble to a powder4 ,if you now measure with a ruler any of the bricks that have not cracked1 you will find that they have shrunk a little and are no longer quite an inch long4 ,this fact is well known to brickmakers2 the moulds in which they make the bricks are larger than the brick is wanted to be4 ,but what would happen if instead of a piece of clay one inch long you had a whole field of clay8 ,would that shrink also1 and1 if so1 what would the field look like8 ,we can answer this question in two ways2 we may make a model of a field and let it dry1 and we can pay a visit to a clay meadow after some hot1 dry weather in summer4 ,the model can be made by kneading clay up under water and then rolling it out on some cardboard or wood as if it were a piece of pastry4 ,cut it into a square and draw lines on the cardboard right at the edges of the clay4 ,then put it into a dry warm place and leave for some days4 ,fig4 #d is a picture of such a model after a week's drying4 ,the clay has shrunk away from the marks1 but it has also shrunk all over and has cracked4 ,if you get an opportunity of walking over a clay field during a dry summer1 you will find similar but much larger cracks1 some of which may be two or three inches wide1 or even more4 ,sometimes the cracking is so bad that the roots of plants or of trees are torn by it1 and even buildings1 in some instances1 have suffered through their foundations shrinking away4 #aa ,we can now understand why some of our model bricks cracked4 ,the cracks were caused by the shrinkage just as happens with our model field4 ,as soon as the clay becomes wet it swells again4 ,a very pretty experiment can be made to show this4 ,fill a glass tube or an egg-cup with dry powdered clay1 scrape the surface level with a ruler1 and then stand in a glass jar full of rain water so that the whole is completely covered4 ,after a short time the clay begins to swell and forces its way out of the egg-cup as shown in ,fig4 #e1 falling over the side and making quite a little shower4 ,in exactly the same way the ground swells after heavy rain and rises a little1 then it falls again and cracks when it becomes dry4 ,darwin records some careful measurements in a book called ,earthworms and ,vegetable ,mould--a large flat stone laid on the surface of a field sank #c4cc millimetres#a whilst the weather was dry between ,may #ith and ,june #acth1 #ab and rose #a4ia millimetres between ,september #gth and #aith of the same year1 much rain having fallen during the latter part of this time4 ,during frosts and thaws the movements were twice as great4 ,illustration3 ,fig4 #d4 ,clay was plastered over a square piece of board and completely covered it4 ,after drying for a week the clay had shrunk and cracked ,you must have found out by now how very slippery clay becomes as soon as it is wet enough4 ,it is not easy to walk over a clay field in wet weather1 and if the clay forms part of the slope of a hill it may be so slippery that it becomes dangerous4 ,sometimes after very heavy rains soil resting on clay on the side of a hill has begun to slide downwards and moves some distance before it stops4 ,fortunately these land slips as they are called1 are not common in ,england1 but they do occur4 ,fig4 #f shows one in the ,isle of ,wight1 and another is described by ,gilbert ,white in ,the ,natural ,history of ,selborne4 ,illustration3 ,fig4 #e4 ,clay swelling up when placed in water and overflowing from the egg-cup into which it was put ,illustration3 ,fig4 #f4 ,landslip in the ,isle of ,wight ,another thing that you will have noticed is that anything made of clay holds water4 ,a simple way of testing this is to put a round piece of tin perforated #ad with holes into a funnel1 press some clay on to it and on to the sides of the funnel 7,fig4 #g71 and then pour on rain water4 ,the water does not run through4 ,pools of water may lie like this on a clay field for a very long time in winter before they disappear1 as you will know very well if you live in a clay country4 ,so when a lake or a reservoir is being made it sometimes happens that the sides are lined with clay to keep the water in4 ,illustration3 ,fig4 #g4 ,a thin layer of clay a entirely prevents the water running through ,if water cannot get through can air8 ,this is very easily discovered3 plug a glass tube with clay and see if you can draw or blow air through4 ,you cannot4 ,clay can be used like putty to stop up holes or cracks1 and so long as it keeps moist it will neither let air nor water #ae through4 ,take two bottles like those in ,fig4 #h1 stop up the bottom tubes1 and fill with water4 ,then put a funnel through each cork and fit the cork in tightly1 covering with clay if there is any sign of a leak4 ,put a perforated tin disk into each funnel1 cover one well with clay and the other with sand4 ,open the bottom tubes4 ,no water runs out from the first bottle because no air can leak in through the clay1 but it runs out very quickly from the second because the sand lets air through4 ,these properties of clay and sand are very important for plants4 ,sow some seeds in a little jar #af full of clay kept moist to prevent it cracking1 and at the same time sow a few in some moist sand4 ,the seeds soon germinate in the sand but not in the clay4 ,it is known that seeds will not germinate unless they have air and water and are warm enough4 ,they had water in both jars1 and they were in both cases warm1 but they got no air through the clay and therefore could not sprout4 ,pure clay would not be good for plants to grow in4 ,air came through the sand1 however1 and gave the seeds all they wanted for germination4 ,illustration3 ,fig4 #h4 ,sand allows air to pass through it1 and so water runs out of the bottle4 ,clay does not let air pass1 and the water is therefore kept in1 even though the tube is open4 ,this also explains something else that you may have noticed4 ,if you tried baking one of your model bricks in the fire you probably found that the brick exploded and shattered to pieces3 the water still left in the brick changed to steam when it was heated1 but the steam could not escape through the clay1 and so it burst the clay4 ,in a brick works the heat is very gradually applied and the steam only slowly forms1 so that it has time to leak away1 then when it has all gone the brick can be heated strongly4 ,you should try this with one of your model bricks2 leave it in a hot place near the stove or on the radiator for a week or more and then see if you can bake it without mishap4 ,let us now compare a piece of clay with a brick4 ,the differences are so great that you would hardly think the brick could have been made from clay4 ,the brick is neither soft nor sticky1 and it has not the smooth surface of a piece of clay1 but is full of little holes or pores1 which look as if they were formed in letting the steam out4 ,a brick lets air through2 some air gets into our houses through the bricks even when the windows are shut4 ,water will get through bricks more easily than it does through clay4 ,after heavy rain you #ag can often find that water has soaked through a brick wall and made the wall paper quite damp4 ,a pretty experiment can be made with the piece of apparatus shown in ,fig4 #i3 bore in a brick a hole about an inch deep and a quarter of an inch wide1 put into the hole the piece of bent glass tubing1 and fix it in with some clay or putty1 then pour some water blackened with ink into the tube1 marking its position with a label4 ,stand the brick in a vessel so full of water that the brick is entirely covered4 ,water soaks into the brick and presses the air out3 the air tries to escape through the tube and forces up the black liquid4 ,illustration3 ,fig4 #i4 ,a brick standing in water4 ,the air in the brick is driven inwards by the water and forces the liquid up the tube in order to escape ,one more experiment may be tried4 ,can a brick be changed back into clay8 ,grind up the brick and it forms a gritty powder4 ,moisten it1 work it with your fingers how you please1 but it still remains a gritty powder and never takes on the greasy1 sticky feeling of #ah pure clay4 ,indeed no one has ever succeeded in making clay out of bricks4 ,all these experiments show that clay is completely altered when it is burnt4 ,we also found that soil is completely altered by burning1 and if you look back at your notes you will see that the changes are very much alike1 so much so that we can safely put down some of the changes in the burnt soil--the red colour1 the hard grittiness1 and the absence of stickiness--to the clay4 ,let us now examine a piece of dry1 but unburnt1 clay4 ,it is very hard and does not crumble1 it is neither sticky nor slippery4 ,directly1 however1 we add some water it changes back to what it was before4 ,drying therefore alters clay only for the time being1 whilst baking changes it permanently4 #a ,a little more than one-eighth of an inch4 #ai ,,chapter ,,iii ,,what ,,lime ,,does ,,to ,,clay ,apparatus required4 ,clay1 about #f lbs4 ,some of the clay from ,chapter ,,ii may1 if necessary1 be used over again4 ,lime1 about #a_/b lb4 ,six funnels1 stands and disks #b4 ,twelve glass jars #b4 ,lime water#a4 ,if you are in a clay country in autumn or early winter you will find some of the fields dotted with white heaps of chalk or lime1 and you will be told that these things improve the soil4 ,we will make a few experiments to find out what lime does to clay4 ,put some clay on to a perforated tin disk in a funnel just as you did on p4 #ad1 press it down so that no water can pass through4 ,then sprinkle on to the clay some powdered lime and add rain water4 ,soon the water begins to leak through1 though it could not do so before2 the addition of the lime1 therefore1 has altered the clay4 ,if you added lime to a garden or a field on which water lay about for a long time in winter you would expect the water to drain away1 especially if you made drains or cut some trenches along which the water could pass4 ,there are large areas in ,england where this has been done with very great advantage4 #bj ,the muddy liquid obtained by shaking clay with water clears quickly if a little lime is stirred in4 ,fill two jars ,a and ,b 7,fig4 #aj7 with rain water1 rub clay into each and stir up so as to make a muddy liquid1 then add some lime water to ,b and stir well4 ,leave for a short time4 ,flocks quickly appear in ,b1 then sink1 leaving the liquid clear1 but ,a remains cloudy for a long time4 ,but why should the liquid clear8 ,we decided in our earlier experiments that the clay floated in the water because it was in very tiny pieces2 when we took a larger lump the clay sank4 ,the lime has for some reason or other1 which we do not understand1 made the small clay particles stick together to form the large flocks1 and these can no longer float1 but sink4 ,if we look at the limed clay in our funnel experiment we shall see that the same change has gone on there2 the clay has become rather loose and fluffy1 and can therefore no longer hold water back4 ,illustration3 ,fig4 #aj4 ,addition of lime to turbid clay water now makes the clay settle and leaves the water quite clear ,lime also makes clay less sticky4 ,knead up one piece of clay with rain water alone and another piece #ba with rain water and about #a_/bj its weight of lime4 ,the limed clay breaks easily and works quite differently from the pure clay4 ,,summary4 ,this1 then1 is what we have learnt about clay4 ,clay is made up of very1 very1 tiny pieces1 so small that they float in water4 ,they stick together when they are wetted and then pressed1 and they remain together2 a piece of clay moulded into any pattern will keep its shape even after it is dried and baked4 ,clay is therefore made into bricks1 earthenware1 pottery1 etc41 whilst white clay1 which is found in some places1 is made into china4 ,wet clay shrinks and cracks as it dries2 these cracks can easily be seen in the fields during dry weather4 ,this shrinkage interferes with the foundations of houses and other buildings1 causing them to settle4 ,dry clay is different from wet clay1 it is hard1 not sticky and not slippery1 but it at once becomes like ordinary clay when water is added4 ,after baking1 however1 clay permanently alters and cannot again be changed back to what it was before4 ,clay will not let water pass through2 a clay field is therefore nearly always wet in winter and spring4 ,nor can air pass through until the clay dries or cracks4 ,lime has a remarkable action on clay4 ,it makes the little1 tiny pieces stick together to form feathery flocks which sink in water2 lime therefore causes muddy clay water to become clear4 ,the flocks cannot hold water back1 and hence limed clay allows water to pass through4 ,limed clay is also less sticky than pure clay4 ,a clay field or garden is improved by adding lime because the soil does not remain wet so long as it did before2 it is also less sticky and therefore more easily cultivated4 #a ,lime water is made by shaking up lime and water4 ,it should be kept in a well-corked bottle4 #bb ,,chapter ,,iv ,,some ,,experiments ,,with ,,the ,,sand ,apparatus required4 ,sand1 about #f lbs42 clay1 about #f lbs4 ,six funnels1 stands and disks #a4 ,six glass jars #b4 ,one box with glass front shown in ,fig4 #ac filled with clay and sand1 as indicated4 ,quarry chalk 7about #e lbs474 ,six beakers #a4 ,six egg-cups #a4 ,if there is a sand pit near you1 or a field of sandy soil1 you should get a supply for these experiments2 if not1 some builder's sand can be used4 ,when the sand is dry you will see that the grains are large and hard4 ,further1 they are all separate and do not stick together2 if you make a hole in a heap of the sand1 the sides fall in1 there is nothing solid about it1 and you can easily see the mistake of the foolish man who built his house upon the sand4 ,when the sand is wet it sticks better and can be made into a good many things2 at the seaside you can make a really fine castle with wet sand4 ,but as soon as the sand dries it again becomes loose and begins to fall to pieces4 ,illustration3 ,fig4 #aa4 ,sand dunes1 ,penhale sands1 ,cornwall ,strong winds will blow these fragments of dry sand about and pile them up into the sand hills or dunes common in many seaside districts 7,fig4 #aa74 ,blowing sands can also be found in inland districts2 in the northern part of ,surrey1 in parts of ,norfolk and many #bd other places are fields where so much of the soil is blown away by strong winds that the crops may suffer injury4 ,in ,central ,asia sand storms do very much harm and have in the course of years buried entire cities4 ,fig4 #ab shows the ,penhale sands in ,cornwall gradually covering up some meadows and ruining them4 ,illustration3 ,fig4 #ab4 ,sand from ,penhale sand dunes blowing on to and covering up meadows ,sand particles1 being large1 do not float in water4 ,if we shake up sand in water the sand sinks1 leaving the water entirely clear4 ,so running water does not carry sand with it unless it is running very quickly3 the sand lies at the bottom4 ,unlike clay1 sand does not hold water4 ,pour some water on to sand placed on the tin disk in a funnel 7,fig4 #h72 it nearly all runs through at once4 ,we should therefore expect a sandy field or a sandy road to dry up very quickly after rain and not to remain wet like a clay field4 ,so much is this the case that people prefer to live on a sandy soil rather than on a clay4 ,the most desirable residential districts round ,london1 ,hampstead on the north1 and the stretch running from ,haslemere on the south-west to ,maidstone on the south-east1 and other favoured regions1 are all high up on the sand4 ,at the foot of a hill formed of sand you often find a spring1 especially if clay or solid rock lies below4 ,it is easy to make a model that will show why the spring forms at this particular place4 ,fill the lower part of the box shown in ,fig4 #ac with wet clay1 smoothing it out so that it touches all three sides and the glass front2 then on top of the clay put enough sand to fill the box4 ,bore four holes in the side as shown in the picture1 one at the bottom1 one at the top1 one just above the junction of the sand and clay1 the fourth half way up the sand1 and fix in glass tubes with clay or putty4 ,pour #bf water on to the sand out of a watering can fitted with the rose so as to imitate the rain4 ,at first nothing seems to happen1 but if you look closely you will notice that the water soaks through and does not lie on the surface2 it runs right down to the clay2 then it comes out at the tube there 7c in the picture74 ,none goes through the clay1 nor does enough stay in the sand to flow out through either the top or the second tube2 of the four tubes only one is discharging any water4 ,the discharge does not stop when the supply of water stops4 ,the rain need only fall at intervals1 but the water will flow all the time4 ,illustration3 ,fig4 #ac4 ,model spring4 ,a box with glass front contains a layer of clay and one of sand4 ,water that falls on the sand runs right down to the clay but can get no further1 and therefore flows out through the tube c at the junction of the clay and the sand4 ,the same result is obtained when chalk takes the place of sand ,the experiment should now be tried with some chalk from a quarry2 it gives the same results and shows that chalk1 like sand1 allows water readily to pass4 ,illustration3 ,fig4 #ad4 ,foot of a chalk hill at ,harpenden where a spring breaks out just under the bush at the right-hand side of the gate ,just the same thing happens out of doors in a sandy or chalky country2 the rain water soaks through the sand or chalk until it comes to clay or solid rock that it cannot pass1 then it stops4 ,if it can find a way out it #bh does so and makes a spring1 or sometimes a whole line of springs or wet ground4 ,rushes1 which flourish in such wet places1 will often be found growing along this line1 and may1 indeed1 in summer time be all you can see1 the water having drained away4 ,but after much rain the line again becomes very wet4 ,fig4 #ad shows the foot of a chalk hill near ,harpenden1 where a spring breaks out just under the bush at the right-hand side of the gate4 ,in ,fig4 #ae the bush itself is seen1 with the little pool of water made by the spring4 ,here the water flows gently1 but elsewhere it sometimes happens1 as in ,fig4 #af1 that the spring breaks out with great force4 ,illustration3 ,fig4 #ae4 ,the little pool below the tree ,now stop up the glass tubes so that the water cannot get out4 ,soon the sand becomes flooded and is no better than clay would be4 ,a second model will show this very well4 ,make a large saucer of clay and fill with sand3 #cj pour water on4 ,the water stays in the sand1 because it cannot pass through the clay4 ,a sandy field saturated like this will therefore not be dry1 but wet1 and will not make a good position for a house4 ,we must therefore distinguish the two cases illustrated in ,fig4 #ag4 ,a shows sand on a hill1 dry because the water runs through until it comes to clay or rock1 when it stops and breaks out as a spring1 a tiny stream1 or pond2 this is a good building site and you may expect to find large houses there4 ,b shows the sand in a basin of clay1 where the water cannot get away3 here the cellars and downstairs rooms are liable to be wet1 and in a village the wells give impure water4 ,matters could be improved if a way out were cut for the water1 but then the foundations of the buildings might move a little4 ,illustration3 ,fig4 #af4 ,water bursting out from an underground spring1 ,old ,cateriag ,quarry1 ,dunbar ,it often happens that villages are situated at the junction of sand and clay1 or chalk and clay1 because the springs furnish forth a good water supply4 ,on the other hand large tracts of clay which remain wet and sticky during a good part of the year are not very attractive to live in1 and even near ,london they were the last to be populated3 ,hither ,green in the south-cast and the clay districts of the north-west have only of late years been built on2 while the sands and gravels of ,highgate1 ,chiswick1 ,brentford and other places had long been occupied4 ,elsewhere1 villages on the clay do not grow quickly unless there is much manufacturing or mining2 the parishes are large1 the roads even now are not good while they used to be very bad indeed4 ,macaulay tells us that at the end of the seventeenth century in some parts of ,kent and ,sussex none but the strongest horses could in winter get through the bog1 in which at every step they sank #ca deep4 ,the markets were often inaccessible during several months4 4 4 ,the wheeled carriages were1 in this district1 generally pulled by oxen4 ,when ,prince ,george of ,denmark visited the stately mansion of ,petworth in wet weather1 he was six hours in going nine miles2 and it was necessary that a body of sturdy hinds should be on each side of his coach to prop it up4 ,of the carriages which conveyed his retinue several were upset and injured4 ,a letter from one of the party has been preserved in which the unfortunate courier complains that1 during fourteen hours1 he never once alighted1 except when his coach was overturned or stuck fast in the mud4 ,the ,romans knew how to make roads anywhere1 and so they made them run in a straight line between the two places they wished to connect1 but the art was lost in later years1 and the country roads made in ,england since their time usually had to follow the sand or the chalk1 avoiding the clay as much as possible4 ,these roads we still use4 ,fig4 #ah shows the roads round ,wye2 you should in your rambles study your own roads and see what soil they are on4 ,illustration3 ,fig4 #ag4 ,two positions of sand4 ,a is dry because the water can drain away and break out as a spring at c4 ,b is wet because the water cannot drain away ,there are several other ways in which sand differs from clay4 ,it does not shrink on drying nor does it #cb swell on wetting1 and you will find nothing happens when you try with sand the experiment with the model field 7p4 #aa7 or the egg-cup 7p4 #ab74 ,illustration3 ,fig4 #ah4 ,the roads round ,wye4 ,as far as possible they keep off the clay 7the plain part of the map7 and keep on the chalk or the sand 7the dotted part of the map7 #cc ,,chapter ,v ,,the ,,part ,,that ,,burns ,,away ,apparatus required4 ,leaf mould4 ,mould from a tree4 ,peat4 ,about #a lb4 soil from a wood1 a well-manured garden and a field2 also some subsoil4 ,six crucibles or tin lids4 ,six tripods1 pipe-clay triangles1 and bunsen burners or spirit lamps4 ,six beakers and egg-cups #a4 ,in the autumn leaves fall off the trees and form a thick layer in the woods4 ,they do not last very long2 if they did they would in a few years almost bury the wood4 ,you can1 in the springtime or early summer find out what has happened to them if you go into a wood or carefully search under a big hedge in a lane where the leaves were not swept away4 ,here and there you come across skeleton leaves where only the veins are left1 all the rest having disappeared4 ,but generally where the leaves have kept moist they have changed to a dark brown mass which still shows some of the structure of a leaf4 ,this is called leaf mould4 ,the top layer of soil in the wood is soft1 dark in colour1 and is evidently leaf mould mixed with sand or soil4 ,leaf mould is highly prized by gardeners1 indeed gardeners will often make a big heap of leaves in autumn and let them rot down and change into mould4 ,if you can in autumn collect enough leaves to make a heap you #cd should do so and leave it somewhere where the rain can fall on it1 but cover it with a few small branches of trees to prevent the wind blowing the leaves away4 ,the heap shrinks a great deal during the first few months1 and in the end it gives a supply of mould that will be very useful if you want to grow any plants in pots4 ,some of the little hollows in the bank under a hedge1 especially on chalky soils1 are filled with leaf mould which has sometimes changed to a black powder not looking at all like leaves4 ,you can also find mould in holes in decayed trees2 here it has formed from the wood of the tree4 ,it appears1 then1 that dead leaves1 etc41 slowly change into a black or brown substance1 shrinking very much as they do so4 ,for this reason they do not go on piling up year after year till finally they fill the wood2 instead they decay or rot down to form leaf mould3 the big pile of the autumn has changed by the next summer to a thin layer which mixes with the soil4 ,we want now to see what happens on a common or a piece of waste ground that is not cultivated4 ,grass and wild plants grow up in summer and die during winter2 their stems and roots are not taken away1 but clearly they do not remain where they are1 because next year new plants grow up4 ,we may suppose that the dead roots and stems decay like the leaves did1 and change to a brown or black mould4 ,it looks as if we are right1 because on digging a hole or examining the side of a freshly cut ditch we shall find that the top layer of soil1 just so far as the living roots go1 is darker in colour than the layer below4 ,we must1 however1 try and get some more proof1 and to do this we must study some of our specimens a little #ce more closely4 ,we will take some leaf mould1 some black mould from a hollow in the bank1 some from a tree1 soils from a wood1 a well-manured garden1 a field and some subsoil4 ,all except the subsoil have a dark colour1 but the wood and garden soils are probably darker than the field soil4 ,now weigh out #b grains of each of these and heat in a dish as you did the soil on p4 #d2 notice that all except the subsoil go black and then begin to smoulder1 but the moulds smoulder more than the soils4 ,then weigh again and calculate how much has burnt away in each case4 ,here are some results that have been obtained at ,harpenden3-- ,amount ,percentage ,colour before of loss on ,colour of burning smouldering burning residue ,leaf mould dark brown much #gh4c light grey ,mould from dead tree black much #fj4f light grey ,soil from wood dark brown less #dc4da white ,soil from garden almost black less #aj4a red ,soil from field brownish still less #e4d red ,subsoil red none #b4j red ,the mould nearly all burns away and its dark colour entirely goes1 so also does the dark colour of the soil4 ,our supposition explains why1 in the case of soils1 the less the blackness1 the less the loss on burning4 ,if the #cf brown or black combustible part is really mould formed by the decay of plant roots1 etc41 then we should expect that as the percentage of mould in the soil increased1 so its blackness would increase and its loss on burning would become greater4 ,this actually happens4 ,this1 then1 is our idea4 ,we suppose that the plants that have lived in past years have decayed to form a black material like leaf mould which stops in the soil1 giving it a darkish colour4 ,the more mould there is1 the darker the colour of the soil4 ,we know that along with this decay there is a great deal of shrinkage4 ,as the black material is formed from the plant1 it only extends as far into the soil as the plant roots go1 so that there is a sharp change in colour about #f inches below the surface 7see also p4 #b74 ,like the plant the black material all burns away when the soil is heated sufficiently4 ,thus we can explain all the facts we have observed1 and in what seems a very likely way4 ,this does not show that our supposition is correct1 but only that it is useful4 ,when you come to study science subjects you will find such suppositions1 or hypotheses as they are called1 are frequently used so long as they are found to be helpful4 ,in our present case we could only get absolute proof that the black combustible part of the soil really arose from the decay of plants by watching the process of soil formation4 ,we shall turn later to this subject4 ,the black material is known as humus4 ,farmers and gardeners like a black soil containing a good deal of humus because they find it very rich1 and we shall see later on why this is so4 ,vast areas of such soils occurring in ,manitoba1 in ,russia1 and in ,hungary are used for #cg wheat growing1 while there are also areas in the ,fen districts of ,england4 ,there is something known as peat that looks rather like mould1 but is really so different that you must be careful not to confuse the two4 ,peat is not good for plants1 and does not make the soil fertile1 but quite the reverse4 ,you can see it being formed on a moor or bog1 and you should at the first opportunity go and examine it4 ,there was a peat bog near ,wye that was examined with the following results4 ,the peat was very fibrous and had evidently been formed from plants4 ,it made a layer about #b feet thick and underneath it was a bed of clay2 this was discovered by examining the ditches1 some of which cut right through the peat into the clay below4 ,a sample of the clay put into a funnel1 as on p4 #ad1 did not allow water to pass through2 this was also evident from the very wet nature of the ground4 ,the peat bed was below the level of the surrounding land and was in a sort of basin2 the water draining from the higher land could all collect there but could not run away1 indeed it might very well have been a shallow lake4 ,it was quite clear that the plants as they died would decay in very wet soil1 and so the conditions are very different from those we have just been studying where the plants decay in soil that is only moist4 ,this difference at once shows itself in the fact that peat generally forms a thick layer1 while mould only rarely does so4 ,in the north of ,england the moors lie high1 but here again the peat bed is like a saucer or basin1 and there is soil or rock below that does not let the rain water pass through4 ,for a great part of the year the beds are very wet4 #ch ,look at a piece of peat and notice how very fibrous it is1 quite unlike leaf mould4 ,when it is dry peat easily burns and is much used as fuel in parts of ,scotland1 ,wales and ,ireland4 ,it is cut in blocks during the spring1 left to dry in heaps during summer1 and then carried away in autumn4 ,fig4 #ai shows a peat bog with cutting going on4 ,peat does not easily catch light and the fires are generally kept burning all night2 there is no great flame such as you get with a coal fire1 but still there is quite a nice heat4 ,peat has a remarkable power of absorbing water4 ,fill an egg-cup with peat1 packing it as tightly as you possibly can1 and then put it under water and leave for some days4 ,the peat becomes very wet and swells considerably1 overflowing the cup just like the clay did on p4 #ab4 ,after long and heavy rains peat in bogs swells up so much that it may become dangerous2 if the bog is on the side of a hill1 the peat may overflow and run down the hill like a river1 carrying everything before it4 ,such overflows sometimes occur in ,ireland and they used to occur in the north of ,england2 you can read about one on ,pendle ,hill in ,harrison ,ainsworth's ,lancashire ,witches4 ,but they do not take place when ditches are cut in the bog so that the water can flow away instead of soaking in2 this has been done in ,england4 ,this great power of absorbing water and other liquids1 so terrible when it leads to overflows1 enables peat to be put to various uses1 and a good deal of it is sold as peat-moss1 for use in stables4 ,illustration3 ,fig4 #ai4 ,cutting and carrying peat for fuel1 ,hoy1 ,orkney ,in the ditches of a peat bog red slimy masses can often be found4 ,they look just like rusty iron1 and in fact they do contain a good deal of iron1 but there are also a number of tiny little living things present4 ,the #dj stones and grit just under the peat are usually white1 all the red material from them having been washed out by the water which has soaked through the peat4 ,then at the ditch these tiny living things take up the red material because it is useful to them4 ,peat or moorland water can also dissolve lead from lead pipes and may therefore be dangerous for drinking purposes unless it is specially purified4 ,when you study chemistry you will be able to show that both peat itself and moorland waters are acid while good mould is not4 ,that is why peat is not good for cultivated plants 7see also p4 #if74 ,other things besides peat are formed when plants decay under water4 ,if you stir up the bottom of a stagnant pond with a stick bubbles of gas rise to the surface and will burn if a lighted match is put to them4 ,this gas is called marsh gas4 ,very unpleasant and unwholesome gases are also formed4 #a ,the top two inches of soil only were collected here1 and there were many leaves1 twigs1 etc4 mixed in4 ,soils from different woods vary considerably4 ,if the sample is taken to a greater depth the loss on burning is much less1 and may be only #e or #f per cent4 #da ,,chapter ,,vi ,,the ,,plant ,,food ,,in ,,the ,,soil ,apparatus required4 ,the pot experiments 7p4 xiii74 ,it is a rare sight in ,england to see land in a natural uncultivated state devoid of vegetation4 ,the hills are covered with grasses and bushes1 the moors with ling and heather1 commons with grass1 bracken and gorse1 a garden tends to become smothered in weeds1 and even a gravel path will not long remain free from grass4 ,it is clear that soil is well suited for the growth of plants4 ,we will make a few experiments to see what we can find out about this property of soil4 ,we have seen that a good deal of the soil is sand or grit1 and we shall want to know whether this1 like soil1 can support plant life4 ,we have also found that the subsoil is unlike the top soil in several ways1 and so we shall want to see how it behaves towards plants4 ,fill a pot with soil taken from the top nine inches of an arable field or untrenched part of the garden2 another with subsoil taken from the lower depth1 #i to #ah inches1 and a third with clean builder's sand or washed sea-sand4 ,sow with rye or mustard1 and thin out when the seeds are up4 ,keep the pots together and equally well supplied with water2 the plants then have as good a chance of growth in one pot as in any other4 #db ,illustration3 ,fig4 #bj4 ,rye growing in surface soil 7,pot #c71 subsoil 7,pot #d71 and sand 7,pot #e7 #dc ,figs4 #bj and #ba are photographs of sets of plants grown in this way2 the weights in grains were3-- ,green weight ,after drying ,rye ,mustard ,rye ,mustard ,plants grown in top soil 7,pot #c7 #ad4e #ag4g #e4f #b4f subsoil 7,pot #d7 #b4i #e4a #a4f #a4a sand 7,pot #e7 #b4j #d4f #j4h #a4j ,illustration3 ,fig4 #ba4 ,mustard growing in surface soil 7,pot #c71 subsoil 7,pot #d71 sand 7,pot #e7 ,the plants in the soil remained green and made steady growth4 ,those in the sand never showed any signs of getting on1 their leaves turned yellow and #dd fell off2 in spite of the care they received1 and the water1 warmth and air given them1 they looked starved1 and that1 in fact1 is what they really were4 ,nor did those in the subsoil fare much better4 ,the experiment shows that the top soil gives the plant something that it wants for growth and that it cannot get either from sand or from the subsoil2 this something we will call plant food4 ,further proof is easily obtained4 ,at a clay or gravel pit little or no vegetation is to be seen on the sloping sides or on the level at the bottom1 although the surface soil is carrying plants that shed innumerable seeds4 ,a heap of subsoil thrown up from a newly made well1 or the excavations of a house1 lies bare for a long time4 ,the practical man has long since discovered these facts4 ,a gardener is most particular to keep the top soil on the top1 and not to bury it1 when he is trenching4 ,in levelling a piece of ground for a cricket pitch or tennis court1 it is not enough to lift the turf and make a level surface2 the work has to be done so that at every point there is sufficient depth of top soil in which the grass roots may grow4 ,how much plant food is there in the top soil8 ,to answer this question we must compare soil that has been cropped with soil that has been kept fallow1 i4e4 moist but uncropped4 ,tip out some of the soil that has been cropped with rye1 and examine it4 ,remove the rye roots1 then replace the soil in the pot and sow with mustard2 sow also a fallow pot with mustard4 ,keep both pots properly watered4 ,the soil that has carried a crop is soon seen to be much the poorer of the two4 ,fig4 #bb shows the plants1 while their weights in grams were3-- #de ,green weight ,after drying ,mustard growing in soil previously cropped with rye1 ,pot #a #ag4h #fb4c ,mustard growing in soil previously uncropped1 ,pot #b #c4c #h4f ,illustration3 ,fig4 #bb4 ,mustard growing in surface soil previously cropped with rye 7,pot #a7 and in surface soil previously uncropped 7,pot #b7 #df ,the rye has taken most of the plant food that was in ,pot #a leaving very little for the second crop4 ,our soil therefore contained only a little plant food1 not more1 in fact1 than will properly feed one crop4 ,but yet it did not seem to have altered in any way1 even in weight1 in consequence of the plant food being taken out4 ,in our experiment the soil was dried and weighed before and after the mustard was grown2 the results were3-- ,pot #b ,pot #b;a lbs4 oz4 lbs4 oz4 ,weight of dried soil before the experiment #f #f #f #g after #f #f #f #f ------ ------ ,difference #j #j #j #a ,the experiment is not good enough to tell us exactly how much plant food was present at the beginning4 ,but we can say that the amount of plant food in the soil is too small to be detected by such weighing as we can do4 ,here is an account of a similar experiment made #cjj years ago by van ,helmont in ,brussels1 and it is interesting because it is one of the first scientific experiments on plant growth3-- ,i took an earthen vessel in which ,i put #bjj pounds of soil dried in an oven1 then ,i moistened with rain water and pressed hard into it a shoot of willow weighing #e pounds4 ,after exactly five years the tree that had grown up weighed #afi pounds and about #c ounces4 ,but the vessel had never received anything but rain water or distilled water to moisten the soil 7when this was necessary71 and it remained full of soil which was still tightly packed1 and lest any dust from outside should have got into the soil it was covered with a sheet #dg of iron coated with tin but perforated with many holes4 ,i did not take the weight of the leaves that fell in the autumn4 ,in the end ,i dried the soil once more1 and got the same #bjj pounds that ,i started with1 less about two ounces4 ,therefore the #afd pounds of wood1 bark and root arose from the water alone4 ,the experiment is wonderfully good and shows how very little plant food there is in the soil4 ,the conclusion is not quite right1 however1 although it was for many years accepted as proof of an ancient belief1 which you will find mentioned in ,kingsley's ,westward ,ho61 that all things arose from water4 ,it is now known that the last sentence should read1 ,therefore the #afd pounds of wood1 bark and root arose chiefly from the water and air1 but a small part came from the soil also4 ,but to return to our experiment with ,pots #a and #b4 ,they had been kept moist before the mustard was sown4 ,did this moisture have any effect on the soil8 ,take two of the pots that have been kept dry and uncropped1 and two that have been kept moist and uncropped1 also one of dry uncropped subsoil and one of moist uncropped subsoil4 ,sow rye or mustard in each pot and keep them all equally supplied with water4 ,it is soon evident that the top soil is richer in plant food than the subsoil1 and the soil stored moist is rather richer than that stored dry1 although the difference here is less marked4 ,in an experiment in which the soils were put up early in ,july and sown at the end of ,september the weights of crops in grams obtained were3-- #dh ,green weight ,after drying ,plants grown in top soil stored in #af4i #b4f moist condition 7,pots #aj #aa7 #ah4i #b4h ,plants grown in top soil stored in #ab4a #a4h dry condition 7,pots #h #i7 #ad4d #a4i ,plants grown in subsoil stored in moist condition 7,pot #ac7 #e4e #j4i ,plants grown in subsoil stored in dry condition 7,pot #ab7 #e4f #j4h ,the crops on ,pots #aj and #aa ought of course to weigh the same1 and so should the crops on ,pots #h and #i4 ,the differences arise from the error of the experiment4 ,in all experimental work1 however carefully carried out or however skilful the operator1 there is some error4 ,there is clearly an increase in crop as a result of storing the surface soil in a moist condition1 showing that additional plant food has been made1 since these pots were put up4 ,on the other hand it does not appear that much plant food has been made in the subsoil during this time4 ,further evidence on this point is given by an experiment similar to that in ,fig4 #bb1 but where mustard is grown in subsoil kept moist1 but uncropped for some time1 and in subsoil previously cropped with rye4 ,the results in grams were3-- ,green weight ,after drying ,mustard growing in subsoil previously cropped with rye #ab4f #b4bg ,mustard growing in subsoil previously uncropped #ab4i #b4bf #di ,these should be compared with the figures on p4 #de4 ,although the subsoil lay fallow for a long time it produced no plant food but is just as poor as the subsoil that has been previously cropped4 ,these observations give us a clue that must be followed up in answering our next question4 ,what has the plant food been made from8 ,clearly it is not made from the sand1 the clay or the chalk since all these occur in the subsoil4 ,we have seen 7,chap4 ,i47 that the top soil differs from the subsoil in containing a quantity of material that will burn away and is in part at any rate made up of plant remains4 ,it will be easy to find out whether these remains furnish any appreciable quantity of plant food4 ,fill one pot with surface soil and another with the same weight of surface soil well mixed up with #cj grams of plant remains--pieces of grass1 or stems and leaves of other plants cut up into fragments about half an inch long4 ,at the same time put up two pots of subsoil1 one of which1 as before1 is mixed with #cj grains of plant remains1 and also put up two pots of sand1 one containing #cj grams of plant remains and the other none4 ,sow all six pots with mustard and keep watered and well tended4 ,the result of one experiment is shown in ,fig4 #bc and the weights of the crop in grams were3-- ,green weight ,after drying ,top soil and pieces of plants 7,pot #f7 #db4j #e4j ,top soil alone 7,pot #c7 #ag4g #b4f ,difference in top soil #bd4c #b4d #ej ,green weight ,after drying ,subsoil and pieces of plants 7,pot #g7 #aj4e #a4i ,subsoil alone 7,pot #d7 #e4a #a4a ,difference in subsoil #e4d #j4h ,illustration3 ,fig4 #bc4 ,pieces of grass1 leaves1 etc4 change into plant food in the surface but not to any great extent in the subsoil4 ,mustard is growing in surface soil 7,pot #c71 in surface soil and pieces of grass 7,pot #f71 in subsoil 7,pot #d71 and in subsoil and grass 7,pot #g7 ,now let us look at these results carefully4 ,the experiment with surface soil shows that the pieces of stem and leaf have furnished a good deal of food to the mustard and have caused a gain of #bd4c grams in the crop4 ,if we knew what the pieces were made of we #ea could push the experiment still further and find out more about plant food1 but this involves chemical problems and must be left alone for the present4 ,we can1 however1 say that plant remains are an important source of plant food1 and since we suppose the black material of the soil to be made of plant remains 7see p4 #cf71 it will be quite fair to say also that this black material1 the humus1 is a source of plant food4 ,we have therefore answered the question we set1 and we can explain some at any rate of the differences between the surface soil and the subsoil4 ,the surface soil contains a great deal of the black material1 which forms plant food1 while the subsoil does not4 ,thus plants grow well on the surface soil and starve on the subsoil4 ,we can also explain why gardeners and farmers speak of black soils as rich soils2 they contain more than other soils of this black material that makes plant food4 ,still further1 we can explain why the farmer often sows plants like mustard1 tares or clover1 and then ploughs them into the ground4 ,they are not wasted1 but they make food for the next crop that goes in4 ,now let us turn to the results of the subsoil experiments4 ,the leaves and stems have increased the crop1 but only by #e4d grams3 they have not been nearly so effective as in the surface soil4 ,it is evident that the mustard did not feed directly on the leaves and stems put in2 if it had there should have been an equal gain in both cases4 ,the leaves and stems clearly have to undergo some change before they are made into plant food and the soil has something to do with this change4 ,after the crops are cut the soils should be tipped out and examined4 ,more of the original pieces of leaf and stem are found in the subsoil than in the surface #eb soil4 ,that is to say1 there has been more change in ,pot #f containing surface soil than in ,pot #g containing subsoil4 ,the something1 whatever it may be1 that changes plant remains like leaves1 stems1 pieces of grass1 roots1 etc4 into plant food therefore acts better in the surface soil than in the subsoil4 ,here then we have another difference between surface and subsoils4 ,,summary4 ,the experimental results obtained in this chapter may now be summed up as follows3-- 7#a7 ,plant food is present in the top soil only and not to any extent in the subsoil4 7#b7 ,there is not much present1 so little indeed that we could not detect it by weighing4 7#c7 ,it is1 however1 always being made in the top soil1 if water is present4 ,only little is made from the subsoil4 7#d7 ,the remains of leaves1 stems1 roots1 etc4 furnish an important source of plant food4 7#e7 ,but they have first to undergo some change1 and the agent producing this change is more active in the top soil than in the subsoil4 7#f7 ,the top soil is much the most useful part of the soil and should never be buried during digging or trenching1 but always carefully kept on top4 #ec ,,chapter ,,vii ,,the ,,dwellers ,,in ,,the ,,soil ,apparatus required4 ,garden soil4 ,six bottles and corks #a4 ,twelve ,erlenmeyer flasks1 #ej c4c4 capacity #b4 ,cotton wool4 ,milk 7about half a pint74 ,leaf gelatine4 ,soil baked in an oven4 ,six saucers #c4 ,the apparatus in ,fig4 #bh 7two lots74 ,wash bottle containing lime water 7,fig4 #bg1 also p4 #ai74 ,in digging a garden a number of little animals are found1 such as earthworms1 beetles1 ants1 centipedes1 millipedes and others4 ,there are also some very curious forms of vegetable life4 ,by carefully looking about it is not difficult to find patches of soil covered with a greenish slimy growth2 they are found best under bushes where the soil is not disturbed1 or else where the soil has been pressed down by a footmark and not touched since4 ,any good soil left undisturbed for a time shows this growth4 ,put some fresh moist garden soil into a bottle and cork it up tightly so that it keeps moist4 ,write the date on the bottle and then leave it in the light where you can easily see it4 ,after a time--sometimes a long1 sometimes a shorter time--the soil becomes covered with a slimy growth1 greenish in colour1 mingled here and there with reddish brown4 ,the longer the #ed soil is left the better4 ,often after several months something further happens2 little ferns begin to grow and they live a very long time indeed4 ,there is at ,rothamsted a bottle of soil that was put up just like this as far back as #ahgd4 ,for a number of years past a beautiful fern has been growing inside the bottle1 and even now it is very healthy and vigorous4 ,if1 instead of being kept moist1 the rich garden soil is left in a dry shed during the whole of the winter so that it gradually loses its moisture1 it will generally show quite a lot of white fluffy growth4 ,all of these living things are very wonderful1 and some1 especially earthworms1 are very useful to gardeners and farmers4 ,after a shower of rain look carefully in the garden or else on a lawn1 common1 or pasture field where the grass is closely grazed by cattle or does not naturally grow long1 and you will find numbers of tiny heaps of soil scattered about4 ,carefully brush away a heap and a little hole is seen1 now hit the ground near it a few times with a stick or stamp on it with your foot and the worm1 if he is near the top1 comes up4 ,when he is safely out of the way dig carefully down with a knife or trowel so as to examine the hole or burrow4 ,at the top you generally find it lined with pieces of grass or leaves that the worm has pulled in2 lower down the lining comes to an end1 but the colour of the burrow is redder than that of the rest of the soil wherever the soil has a greenish tinge4 ,these holes are useful because they let air and water down into the soil4 ,illustration3 ,fig4 #bd4 ,soil in which earthworms have been living and making burrows ,the following experiment shows what earthworms can do4 ,fill a pot with soil from which all the worms have been carefully picked out and another #ee with soil to which earthworms have been added1 one worm to every pound of soil4 ,leave them out of doors where the rain can fall on to them4 ,you can soon see the burrows and the heaps of soil or casts thrown up by the worms3 these casts wash or blow over the surface of the soil1 continually covering it with a thin layer of material brought up from below4 ,consequently the soil containing earthworms always has #ef a fresh clean look4 ,after some time the other soil becomes very compact and is covered with a greenish slimy growth4 ,when this happens carefully turn the pots upside down1 knock them so as to detach the soil and lift them off4 ,the soil where the earthworms had lived is full of burrows and looks almost like a sponge4 ,fig4 #bd shows what happened in an experiment lasting from ,june to ,october4 ,the other soil where there were no earthworms shows no such burrows and is rather more compact than when it was put in4 ,earthworms therefore do three things3-- 7#a7 ,they make burrows in the ground and so let in air and water4 7#b7 ,they drag leaves into the soil and thus help to make the mixture of soil and leaf mould4 7#c7 ,they keep on bringing fresh soil up to the surface1 and they disturb the surface so much that it is always clean and free from the slimy growth4 ,all these things are very useful and so a gardener should never want to kill worms4 ,the great naturalist1 ,darwin1 spent a long time in studying earthworms at his home in ,kent and wrote a very interesting book about them1 called ,earthworms and ,vegetable ,mould4 ,he shows that each year worms bring up about #a_/ejth of an inch of soil1 so that if you laid a penny on the soil now and no one took it1 in #ej years it might be covered with an inch of soil4 ,pavements that were on the surface when the ,romans occupied ,britain are now covered with a thick layer of soil4 ,illustration3 ,fig4 #be4 ,fresh soil turns milk bad1 but baked soil does not ,but besides these there are some living things too small to see1 that have only been found by careful experiments1 but you can easily repeat some of these #eg experiments yourselves4 ,divide a little rich garden soil into two parts and bake one in the kitchen oven on a patty tin4 ,pour a little milk into each of two small flasks1 stop up with cotton wool 7see ,fig4 #be7 and boil for a few minutes very carefully so that the milk does not boil over1 then allow to cool4 ,next carefully take out the stopper from one of the flasks and drop in a little of the baked soil1 label the flask baked soil and put back the stopper4 ,into the other flask drop a little of the untouched soil and label it2 leave both flasks in a warm place till the next day4 ,carefully open the stoppers and smell the milk3 the baked soil has done nothing and the milk smells perfectly sweet2 the unbaked soil1 on the other hand1 has made the milk bad and it smells like cheese4 ,if you have a good microscope you can go further3 look at a drop of the liquid from each flask and you find in each case the #eh round fat globules of the milk1 but the bad milk contains in addition some tiny creatures1 looking like very short pins1 darting in and out among the fat globules4 ,these living things must have come from the unbaked soil or they would have been present in both flasks3 they must also have been killed by baking in the oven4 ,illustration3 ,fig4 #bf4 ,soils contain tiny things that grow on gelatine ,another experiment is easy but takes a little longer to show4 ,mix two sheets of leaf gelatine with a quarter #ei of a pint of boiling water1 pour into each of three saucers1 and cover over with plates4 ,then stir up some baked soil in a cup half full of cold boiled water1 and quickly put a teaspoonful of the liquid into a second cup1 also half full of cold boiled water4 ,stir quickly and put a spoonful on to the jelly1 tilting it about so that it covers the whole surface and label the saucer baked soil4 ,do the same with the unbaked soil1 labelling the saucer2 leave the third jelly alone and label it untouched4 ,cover all three with plates and leave in a warm place4 ,after a day or so little specks begin to appear on the jelly containing the unbaked soil1 but not on the others 7,fig4 #bf72 they grow larger1 and before long they change the jelly to a liquid4 ,the other jellies #fj show very few specks and are little altered4 ,these creatures making the specks came from the soil because so few are found on the jelly alone2 they were killed in the baking and so do not occur on the baked soil jelly4 ,illustration3 ,fig4 #bg4 ,bottle containing lime water1 used to show that breath makes lime water milky ,you can also show that breathing is going on in the soil even after you have picked out every living thing that you can see4 ,first of all you must do a little experiment with your own breathing so that you may know how to start4 ,shake up a little fresh lime with water and leave it to stand for #bd hours4 ,pour a little of the clear liquid into a flask or bottle fitted with a cork and two tubes1 one long and one short like that shown in ,fig4 #bg4 ,then breathe in through the tube ,a so that the air you take in comes through the lime water3 notice that no change occurs4 ,next breathe out through the tube ,b so that your breath passes through the lime water2 this time the lime water turns very milky4 ,you therefore alter in some way the air that you breathe3 you know also that you need fresh air4 ,now we can get on with our soil experiments4 ,take two small flasks of equal size fitted with corks and joined by a glass tube bent like a ,u with the ends curled over4 ,put some lime water into each flask and a little water in the ,u-tube4 ,now make a small muslin bag like a sausage3 fill it with moist fresh garden soil1 tie it up with a silk thread and hang it in one of the flasks by holding the end of the thread outside and pushing in the cork till it is held firmly 7see ,fig4 #bh74 ,fix on the other flask1 and after about five minutes mark the level of the liquid with a piece of stamp paper2 leave in a warm place but out of the sun4 #fa ,in one or two days you will see that the water in the ,u-tube has moved towards the soil flask1 showing that some air has been used up by the soil2 further1 the lime water has turned milky4 ,but in the other flask1 where there is no soil1 the lime water remains quite clear4 ,this proves1 then1 that some of the tiny creatures want air just as much as we do4 ,the air readies them through passages in the soil1 through the burrows of earthworms and other animals1 or by man's efforts in digging and ploughing4 ,illustration3 ,fig4 #bh4 ,a bag of soil is fixed into a flask containing lime water4 ,in a few days some of the air has been used up1 and the lime water has turned milky ,now try the experiment with very dry garden soil3 little or no change takes place4 ,as soon as you add water1 however1 breathing begins again1 air is absorbed and the lime water turns milky just as before4 ,water is therefore wanted just as much as air4 ,if you had very magnifying eyes and could see things so enlarged that these little creatures seemed to #fb you to be an inch long1 and if you looked down into the soil1 it would seem to you to be an extraordinarily wonderful place4 ,the little grains of soil would look like great rocks and on them you would see creatures of all shapes and sizes moving about1 and feeding on whatever was suitable to them1 some being destroyed by others very much larger than themselves1 some apparently dead or asleep1 yet waking up whenever it becomes warmer or there was a little more moisture4 ,you would see them changing useless dead roots and leaves into very valuable plant food2 indeed it is they that bring about the changes observed in the experiments of ,chap4 ,,vi4 ,occasionally you would see a very strange sight indeed--a great snake-like creature1 over three miles long and nearly half a mile round1 would rush along devouring everything before it and leave behind it a great tunnel down which a mighty river would suddenly pour1 and what do you think it would be8 ,what you now call an earthworm and think is four inches long1 going through the soil leaving its burrow along which a drop of water trickles6 ,that shows you how tiny these little soil creatures are4 ,these busy little creatures are called micro-organisms because of their small size4 ,but they are not all useful4 ,some can turn milk bad as we have already seen1 and therefore all jugs and dishes must be kept clean lest any of them should be present4 ,others can cause disease4 ,it has happened that a child who has cut its finger and has got some soil into the cut1 and not washed it out at once1 has been made very ill4 ,you may sometimes notice sheep limping about in the fields1 especially in damp fields2 an organism gets into the foot and causes trouble4 #fc ,,summary4 ,the soil is full of living things1 some large like earth worms1 others very small4 ,earthworms are very useful3 they make burrows in the soil1 thus allowing air and water to get in3 they drag in leaves and they keep on covering the surface with soil from below4 ,besides these and the other large creatures1 there are micro-organisms so small that they cannot be seen without a very good microscope3 they live and breathe and require air1 water and food4 ,some are very useful and change dead parts of plants or animals into valuable plant food4 ,almost anything that can be consumed by fire can be consumed by them4 ,others are harmful4 #fd ,,chapter ,,viii ,,the ,,soil ,,and ,,the ,,plant ,apparatus required4 ,dry powdered soil1 sand1 clay1 leaf mould1 seeds4 ,six funnels1 disks1 stands and glass jars #c4 ,six glass tubes about #a_/b in4 diameter and #ah in4 long #b4 ,muslin1 string1 three beakers4 ,six lamp chimneys standing in tin lids #c4 ,pot experiments 7p4 xiii71 growing plant4 ,two test tubes fitted with split corks 7,fig4 #ce74 ,if you have ever tried to grow a plant in a pot you must have discovered that it needs much attention if it is to be kept alive4 ,it wants water or it withers2 it must be kept warm enough or it is killed by cold2 it has to be fed or it gets yellow and starved2 also it needs fresh air and light4 ,these five things are necessary for the plant3 ,water1 ,warmth1 ,food1 ,fresh air1 ,light4 ,we may add a sixth3 there must be no harmful substance present in the soil4 ,wild plants growing in their native haunts get no attention and yet their wants are supplied4 ,we will try and find out how this is done4 #fe ,illustration3 ,fig4 #bi4 ,loam and sand both retain water1 but loam better than sand ,water comes from the rain1 but the rain does not fall every day4 ,how do the plants manage to get water on dry days8 ,a simple experiment will show you one way4 ,put about four tablespoonsful of dry soil on to the funnel shown in ,fig4 #bi and then pour on two tablespoonsful of water4 ,measure what runs through4 ,you will find it very little2 most of the water sticks to the soil4 ,even after several days the soil was still rather moist4 ,soil has the power of keeping a certain amount of water in reserve for the plant1 it only allows a small part of the rain to run through4 ,do the experiment also with sand1 powdered clay1 and leaf mould4 ,some water always remains behind1 but less in the case of sand than in the others4 ,in one #ff experiment #cj cubic centimetres of water were poured on to #ej grains of soil but only #aj cubic centimetres passed through1 but when an equal amount was poured on to #ej grains of sand no less than #bj cubic centimetres passed through4 ,very sandy soils1 therefore1 possess less power of storing water than do soils with more clay or mould in them1 such as loams1 clays or black soils4 ,illustration3 ,fig4 #cj4 ,water can rise upwards in soil4 ,it can1 in fact1 travel in any direction1 from wet to dry places ,further1 water has a wonderful power of passing from wet places to dry places in the soil4 ,tie a piece of muslin over the end of a tube and fill with dry soil1 tapping it down as much as you can1 then stand the tube in water as in ,fig4 #cj4 ,fill another with sand #fh and place in water4 ,notice that the water at once begins to rise in both tubes and will go on for a long time1 always passing from the wet to the dry places4 ,it rises higher in the soil than it does in the sand4 ,enough water may pass up the tube in this way to supply the needs of a growing plant4 ,fill a glass lamp chimney with dry soil1 packing it down tightly1 put into water and then sow with wheat4 ,the plants grow very well4 ,a longer tube may be made from two chimneys fastened together by means of a tin collar stuck on with ,canada balsam or sealing wax 7,fig4 #ca74 ,our plants grew well in this also1 but on a sandier soil1 where the water could not rise so high1 it might happen that they would not4 ,illustration3 ,fig4 #ca4 ,wheat growing in soils supplied from below with water4 ,all the water the plant gets has to travel upwards ,thus we shall expect great differences in the moisture of various soils4 ,in some districts there is much more rain than in others1 and therefore the soils get a larger supply of water4 ,sandy soils allow water to run through while a loam holds it like a sponge1 in a loam also the water readily moves from wet to dry places4 ,further1 water runs down hills and collects in low-lying hollows or valleys2 here1 therefore1 the soil is moister than it is somewhat higher up4 ,what will be the effect of these moisture differences on plants8 ,you must find out in two ways4 ,visit a soil that you know is dry--a sandy1 gravelly or chalky soil in a high situation--and look carefully at the plants there1 then go to some moister1 lower ground and see what the plants show4 ,you cannot be quite certain1 however1 that anything you see is simply due to water supply1 because there may be other differences in the soil as well4 ,so you must try the second method1 and that is to find out by experiments what is the effect of varying #fi quantities of water on the plant growth4 ,both methods must be used1 but it may be more convenient to start the experiments first1 and while they are going on to collect observations in your rambles4 ,illustration3 ,fig4 #cb4 ,mustard growing in soils supplied with varying quantities of water4 #af very little water1 #c a nice amount of water1 #ae too much water ,fill four glazed pots with dry soil3 keep one dry2 one only just moist2 the third is to be very moist and should be watered more frequently than the second2 and the fourth is to be kept flooded with water1 any way out being stopped up4 ,sow wheat or mustard in all four and keep out of the rain4 ,the result of one experiment with mustard is shown in ,fig4 #cb4 ,where no water was supplied there was no growth and the seeds remained unaltered4 ,where only little water was supplied 7,pot #af7 the plants made some growth1 but not very much3 the leaves were small and showed no great vigour2 #gj where sufficient water was given 7,pot #c7 the plants grew very well and had thick stems and large leaves2 where too much water was given 7,pot #ae7 the plants were very sickly and small4 ,the weights were3-- ,green weight ,after drying ,plants with too much water #c4i #j4e too little water #e4c #j4i a nice quantity of water #ag4g #b4f ,fig4 #cc shows two pots of wheat1 one kept only just sufficiently moist for growth1 the other kept very moist but not too wet4 ,you can see what a difference there is2 in the drier pot the leaves are rather narrow and the plants are small1 in the moister pot the leaves are wide and the plants big4 ,but there was also another difference that the photograph does not bring out very well--the plants in the rather dry soil were1 as you can see1 in full ear1 ripe and yellow1 while those in the very moist soil were still green and growing4 ,we see then 7#a7 that on moist soils there is greater growth than on dry soils1 but the plants do not ripen so quickly2 7#b7 in very wet soils mustard--and many other plants also--will not grow4 ,water is not itself harmful4 ,it is easy to grow many plants in water containing the proper food1 but air must be blown through the water at frequent intervals4 ,in the water-logged soil of ,pot #ae the trouble arose not from too much water but from too little air4 ,air is wanted because plants are living and #ga breathing in every part1 in the roots as well as in the leaves4 ,illustration3 ,fig4 #cc4 ,this wheat growing on very moist soil was still green and growing vigorously1 whilst this wheat growing on rather dry soil was yellow and ripe ,now turn to what you have seen in your walks4 ,you would probably notice that on the drier1 sandy or gravel ground there was nothing like as great a growth of grass or of other plants as on the moister soil4 ,this is so much like what we found in the pot experiments that we shall not be wrong in supposing that the difference in water supply largely accounted for the difference in growth4 ,but you may also have noticed something else4 ,plants in the drier soil have generally #gb narrow leaves and the grasses are rolled up and fine1 whilst those on the damp soil1 including the grasses1 have usually broad leaves4 ,thus in the dry sandy soil you may find broom1 spurrey1 sheep's fescue1 pine trees1 all with narrow leaves2 whilst on the moister soil you may find burdock1 primroses1 cocksfoot and other broad-leaved plants4 ,figs4 #cd a and b show some plants we found on a dry1 gravelly patch on ,harpenden common1 and on a moist loam in the river valley below4 ,illustration3 ,fig4 #cd a4 ,plants collected on dry sandy soil4 ,broom1 sheep's fescue1 crested dogstail and gorse1 all with narrow leaves #gc ,before we can account for this observation1 we must ascertain a little more closely what becomes of the water the plant takes up4 ,it certainly does not all stay in the plant1 and the only way out seems to be through the leaves4 ,put a test tube on the leaf of a growing plant and fix a split cork round the stem3 leave in sunlight for a few hours and notice that water begins to collect in the test tube 7,fig4 #ce74 ,the experiment shows that water passes out of the plant through the leaves4 ,illustration3 ,fig4 #cd b4 ,plants collected on moist loam4 ,all have wide leaves ,this experiment was first made by ,stephen ,hales1 and described by him thus in #agbg3 ,having by many #gd evident proofs in the foregoing experiments seen the great quantities of liquor that were imbibed and perspired by trees1 ,i was desirous to try if ,i could get any of this perspiring matter2 and in order to do it1 ,i took several glass chymical retorts1 b a p ,fig4 #cf and put the boughs of several sorts of trees1 as they were growing with their leaves on1 into the retorts1 stopping up the mouth p of the retorts with bladder4 ,by this means ,i got several ounces of the perspiring matter of vines1 figtrees--and other trees1 which matter ,hales found to be almost pure water4 ,the test tube experiment should now be made with a narrow-leaved grass like sheep's fescue and with a wide-leaved grass like cocksfoot4 ,you will find that wide-leaved plants pass out more water than those with narrow leaves1 and hence wide-leaved plants occur in damp situations or on damp soils like loams and clays1 while narrow-leaved plants can grow on dry1 sandy soils4 ,illustration3 ,fig4 #ce4 ,plants give out water through their leaves ,another thing you will notice is that fields lying at the side of a river and liable to be flooded1 and fields #ge high up in wet hill districts1 are covered with grass4 ,in a clay country there is also a great deal of grass land and not much ploughed land2 if you live where there is much clay you can easily discover the reason4 ,clay becomes very wet and sticky when rain falls1 and very hard in dry weather3 it is1 therefore1 difficult to cultivate4 ,farmers cannot afford to spend too much money on cultivation1 and so they prefer grass1 because once it is established it goes on indefinitely and does not want ploughing up and re-sowing4 ,and besides1 farmers have learned by experience that grass can tolerate more water and less warmth than most other ,english crops4 ,there is much more grass land in those parts of ,england where the rainfall is high and the temperature rather #gf low--e4g4 the northern parts of ,england--than in the eastern counties where the rainfall is low4 ,illustration3 ,fig4 #cf4 ,stephen ,hales's ,experiment 7from ,vegetable ,staticks1 ,vol4 ,i4 #agbg7 ,the difference in water supply1 therefore1 leads us to expect the following differences between sandy soils and clays or loams3-- ,on sandy soils 7the water content being small7 the wild plants and trees usually have small leaves4 ,cultivated plants do not give very heavy crops1 but they ripen early4 ,on clay soils 7the water content being good7 wild plants and trees usually have larger leaves4 ,cultivated plants give good crops1 but they ripen rather late4 ,if the water content is too good or the clay is too sticky the land is generally put into grass4 ,illustration3 ,fig4 #cg4 ,hill slope near ,harpenden4 ,woodland at the top1 arable land lower down4 ,in the valley there is grass land but this is hidden by the cottages ,plants require to be sufficiently warm4 ,some like tropical heat and can only be grown in hot houses2 others can withstand a certain amount of cold and will grow up on the mountains4 ,our common cultivated crops come in between and will not grow in too cold or exposed a situation2 thus you find very little cultivated land #hjj ft4 above sea level1 and not usually much above #ejj ft4 ,at this height it is left as grass land1 and higher up as woodland1 moor1 or waste land4 ,grass requires less warmth and can therefore grow at greater heights than many other crops4 ,if you start at the top of a hill in ,derbyshire1 and walk down1 you will see that the top is moorland1 lower down comes grass land1 still lower you may find arable land1 and if the valley is damp you will find more grass at the bottom4 ,figs4 #cg and #ch show typical views of the hill slopes further south3 they are taken near ,harpenden4 ,the top of the hill in each case is over #djj ft4 above sea level1 and has never been thought worth cultivating1 but has always been left as #gh wood because it is too exposed for farm crops4 ,on the lower slopes the arable fields are seen1 while at the bottom bordering the river is rough grass land1 shown in ,fig4 #ci4 ,the top is too cold and windy1 and the bottom too wet1 to be worth cultivating4 ,illustration3 ,fig4 #ch4 ,view further along the valley1 woodland and arable above rough grass land near the river ,as the plant root is alive it wants air4 ,the effect of keeping air out can be seen by sowing some barley or onion seeds in the ground and then pouring a lot of water on and plastering the soil down with a spade4 ,sow another row in nicely crumbled soil1 not too wet1 press the seeds well in1 but do not plaster the soil4 ,this second lot will generally do much better than the first4 ,if the ground round a plant is frequently trodden so that it becomes very hard the plant makes much less growth than if the soil were kept nice and loose4 ,a good gardener takes very great pains in preparing his ground before he sows his seeds1 and he is careful that no one should walk on his beds lest his plants should suffer4 ,,summary4 ,we may now collect together the various things we have learnt in this chapter4 ,plants require water1 air1 warmth1 food1 and light1 and they will not grow if harmful substances are present4 ,the rain-water that falls remains for some time in the soil1 and does not at once run away or dry off3 water can also move from wet to dry places in the soil4 ,therefore the plant does not need rain every day1 but can draw on the stock in the soil during dry weather4 ,a sandy soil is usually drier than a loam or a clay1 especially if it lies rather high3 plants growing on a sandy soil make less growth and have narrower and smaller leaves than those on a moister soil4 ,situations more than five or six hundred feet above sea level are1 in ,england1 as a rule1 too bleak and #hj exposed for the ordinary cultivated crops4 ,such land is1 therefore1 either grass land1 moorland1 downland or woodland4 ,the roots of plants are living and require air4 ,the soil must not be trodden too hard round them or air cannot get in1 nor can it if too much water is present4 ,grass can put up with more water and less warmth than most cultivated crops4 ,illustration3 ,fig4 #ci4 ,rough grass pasture near the river1 above that is arable land and still higher is woodland ,instances of these facts may be found in going down any hill #ejj ft4 or more in height3 the top is usually wood or waste1 being too cold for crops1 below this may come grass land1 lower still arable land4 ,it is both warmer and moister in the valley 7since water runs down hill71 and so we can account for the proverbial fertility of valleys4 ,but just near the river1 if there is one1 the ground may be too wet for crops1 and therefore grass is grown4 ,clay land that is rather too wet to plough is usually left in grass4 #hb ,,chapter ,,ix ,,cultivation ,,and ,,tillage ,apparatus required4 ,plot experiments1 hoeing and mulching4 ,thermometer4 ,soil sampler 7,fig4 #db1 p4 #hh74 ,this tool consists of a steel tube #b in4 in diameter and #i in4 long1 with a slit cut along its length and all the edges sharpened4 ,the tube is fixed on to a vertical steel rod1 bent at the end to a ring #b in4 in diameter1 through which a stout wooden handle passes4 ,it is readily made by a blacksmith4 ,farmers and gardeners throughout the spring1 summer and autumn1 are busy ploughing or digging1 hoeing or in other ways cultivating the soil4 ,unless all this is well done the soil fails to produce much2 the sluggard's garden has always been a by-word and a reproach4 ,in trying to understand why they do it we must remember that plant roots need water1 warmth and air2 if the soil is too compact or if there is too much water the plant suffers1 as we have seen4 ,illustration3 ,fig4 #dj4 ,after harvest the farmer breaks up his land with a plough and then leaves it alone until seed time ,one great object of cultivation is1 therefore1 to prevent the soil being too compact and too wet4 ,after the harvest the farmer breaks up his ground with a plough and then leaves it alone till seed time 7,fig4 #dj74 ,a gardener does the same thing with a fork in his kitchen garden--he cannot very well elsewhere1 or the plant roots might #hc become too cold4 ,if there is frost during the winter both farmer and gardener are pleased because they say the frost mellows the ground2 you can see what they mean if you walk on a frosty morning over a ploughed field4 ,the large clods of earth are no longer sticky1 they already show signs of breaking up1 and if they are not frozen too hard can easily be shattered by a kick4 ,the change has been brought about in exactly the same way as the bursting of water-pipes by frost4 ,when water freezes it expands with enormous force and bursts open anything that confines it2 water freezing in the pores of the soil forces the little fragments apart4 ,this action is so important that further illustrations should be looked for4 ,a piece of wet chalk left out on a frosty night often crumbles to pieces4 ,it is dangerous #hd to climb cliffs in the early spring because pieces of rock that have been split off during the winter frosts by the expanding water may easily give way4 ,frost plays havoc with walls built of flints and with old bricks that are beginning to wear4 ,if there are several frosts1 with falls of rain or snow and thaws coining in between1 the soil is moved about a good deal by the freezing and melting water4 ,bulbs and cuttings are sometimes forced out of the ground1 whilst grass and young wheat may be so loosened that they have to be rolled in again as soon as the weather permits4 ,when the ground has been dug in autumn and left in a very rough state all this loosening work of the frost is very much helped1 because so much of the soil may become frozen4 ,if in spring you dig a piece of land that has already been dug in autumn1 and then try digging a piece that has not1 you will find the first much easier work than the second in all but very sandy soils4 ,a little before the seeds are sown1 the soil has to be dug or cultivated again so that it may become more level and broken into smaller pieces4 ,the farmer then harrows and the gardener rakes it1 and it becomes still finer4 ,very great care is bestowed on the preparation of the seed bed1 and it will take you longer to learn this than any other part of outdoor gardening4 ,the soil has to be made fine and dry1 and no pains must be spared in getting it so4 ,when at last the soil is fine enough the seed is put in4 ,but it is not enough simply to let the seed tumble into the ground4 ,it has to be pressed in gently with a spade or a roller1 not too hard or the soil becomes too sticky4 ,fig4 #da shows this operation being carried out on the farm4 ,then the soil should be left alone4 ,illustration3 ,fig4 #da4 ,rolling in mangold seeds on the farm #hf ,if you watch an allotment holder who grows onions really well working away at his seed-bed you will see what a beautifully fine tilth he gets4 ,if you try to do the same you will probably fail2 his seeds will be up before yours and will grow into healthier plants4 ,only after long practice will you succeed1 and then you will have mastered one of the great mysteries of gardening4 ,as soon as the plants are up they have to be hoed1 and the more often this is done the better4 ,hoeing has several useful effects on the soil2 during summer time some experiments may be made to find out what these are4 ,a piece of ground is wanted that has got no crop on it4 ,set out three strips each six feet wide and six feet long1 leave one entirely alone1 hoe the second once a week1 and the third three times a week2 put labels on so that no mistake can arise4 ,the surface of the untouched plot becomes very compact and glazed in appearance2 the other soils look nice and crumbly4 ,take the temperature of the soils by placing a thermometer into it at various depths--half inch1 three inches1 and six inches--also take the temperature of the air2 enter up the results as in the table1 which shows what happened at ,harpenden4 ,air ,date temperature ,soil temperature ,hoed ,hoed ,untouched once three times weekly weekly #aiaj ,june #bjth #cj #a_/b inch #ce #ca4e #ca4e #c inches #cj4e #bi4h #bh4h #f inches #bg #bf4e #bd ,june #bgth #ah #a_/b inch #ag4e #ag #ag #c inches #af4g #af4c #af4b #f inches #ae4h #ae4e #ae4f #hg ,the thermometer readings are in degrees centigrade4 ,remarks4 ,june #bjth3 ,hot sunny day1 there had been no rain since ,june #aath4 ,june #bgth3 ,cold1 cloudy day1 several cold1 wet days during the past week4 ,on the cold day there was very little difference between the plots1 but on the hot day the hoed plots were cooler than the others4 ,now only the top inch is touched by the hoe1 and so it appears that the layer thus loosened shields the rest of the soil from the sun's heat4 ,if this is the case we ought to find that any other loose material would act in just the same way4 ,we must1 therefore1 set out a fourth plot alongside the others1 cover it with straw or cut grass 7a cover like this is called a mulch71 and take the temperature there4 ,some of the results were as follows3-- ,air ,date temperature ,soil temperature ,hoed plot ,mulched plot #aiaj ,sept4 #bdth #ae #a_/b inch #ag4e #ab4be #c inches #ab4e #aa4ge #f inches #ab4be #aa4e ,oct4 #eth #ag #a_/b inch #ag #ae4e #c inches #af4g #ae #f inches #ae4e #ad4e ,remarks4 ,sept4 #bdth3 ,warm day after a rather cold spell4 ,oct4 #eth3 ,after a long spell of dry1 warm weather4 ,the untouched plot had become smothered in weeds and could no longer be used for this experiment4 ,the mulched soil is1 however1 cooler even than the hoed soil1 and our expectation that mulching would keep the soil cool has turned out to be correct4 #hh ,illustration3 ,fig4 #db4 ,soil sampler4 7,see p4 #hb for description7 ,it may be expected that the hotter soil--the unhoed plot--will also be drier than the others1 and this can be found out by a simple experiment4 ,take a sample by making a hole six indies deep with straight and not with sloping sides3 this is best done by driving a tube two inches wide into the soil 7,fig4 #db73 if you have not got such a tool you may use a trowel1 but you will have to be very quick and very careful4 ,weigh the soil--or a part of it if you have got a great deal--then set it to dry in a warm place for three or four days4 ,weigh again when it is dry3 the difference gives the loss of water3 find what it would be in a hundred parts4 ,our results were3-- #hi ,date ,percentage of water in the ,untouched soil ,soil hoed once ,soil hoed three weekly times weekly #aiaj ,june #dth #ba4a #ai4e #ag4i ,june #bjth #ad4g #af4j #af4j ,june #bgth #ai4c #ah4d #bj4e ,remarks4 ,june #dth2 ,the weather is still cold and the summer has not yet begun4 ,june #bjth3 ,hot day following on some hot1 dry weather4 ,june #bgth3 ,rain had recently fallen4 ,when hoeing is done in the early part of the summer it dries the soil1 and the more frequent the hoeing the drier the soil 7see ,june #dth results74 ,but later on1 when the hot weather begins1 the hoed soil loses much less moisture than the untouched plot2 the latter lost #f4d per cent4 in #af days in the top six inches1 whilst the soil hoed once weekly lost #c4a per cent41 and the one hoed three times weekly lost only #a4d2 the two hoed soils are now equal1 and are both moister than the untouched soil4 ,when more rain comes they get just as wet as the others3 hoeing does not prevent water from sinking in1 but it does prevent water from getting lost4 ,our experiment has1 therefore1 shown us that hoeing makes a loose layer of soil which shields the rest of the soil from the sun's heat1 and prevents it getting too hot or too dry4 ,a hoed soil is cooler and moister1 and therefore better suited for the growth of plant roots than an unhoed soil4 #ij ,the mulch of straw or dried grass was found to have the same effect in conserving the water as the loose layer of soil obtained by hoeing4 ,some results were3-- ,percentage of moisture in ,date ,hoed soil ,mulched soil #aiaj ,sept4 #bdth #ai4f #bj4g ,illustration3 ,fig4 #dc4 ,cultivation and mulching reduce the loss of water from soils ,these results are so important that some indoor experiments should be made to furnish more proof4 ,fix up three inverted bell jars with corks and bent tubes as shown in ,fig4 #dc1 fill all with dry soil well pressed down1 then add water carefully till it appears in the glass tubes4 ,next day mark with stamp paper the level of liquid in each tube and then leave one jar #ia untouched1 carefully cultivate with a penknife every two or three days the top quarter of an inch of the second1 and cover the third with a layer of grass4 ,after a week notice again the levels of the liquid and mark with paper2 you find that the water has fallen most in the untouched jar1 showing that more has been lost from this than from the jars covered with a mulch either of soil or of dry grass4 ,a slate or flat stone acts like a mulch2 if you leave one on the soil for a few days in hot weather and then lift it up on a hot day you will see that the soil underneath is quite moist2 you may also find several slugs or other animals that have gone there for the sake of the coolness and the moisture4 ,plants and trees also keep off the sun's heat and so make the soil cold and moist4 ,grass land is in summer and autumn1 and even in early winter1 cooler near the surface than bare land4 ,at ,harpenden we found3-- ,soil temperature ,date ,grass land ,bare land #aiaj ,sept4 #bdth #a_/b inch #ac #ag4e #c inches #ab4e #ab4e #f inches #ab4e #ab4be ,oct4 #eth #a_/b inch #ag4e #ag #c inches #ae #af4g #f inches #ad4e #ae4e ,even if the ground is not covered a certain amount of protection is still possible4 ,trees are often planted round ponds to prevent evaporation of the water4 ,the wind helps to dry the soil very much1 and a hedge #ib that shields from the wind not only protects the crop but also keeps the soil moist3 a road with high hedges at each side remains wet for a long time after more exposed parts have dried4 ,the effect on the temperature can be well seen on a day when a ,n4,e4 wind is blowing4 ,fix up on a piece of the experimental ground a little hedge made of small pea-stakes or brushwood1 and take the soil temperature at one inch depth1 both on the windward and on the leeward side4 ,two results were3-- ,temperature at #a inch depth--sheltered side #ae4e windward side #ad ,we have already seen that on the hot day1 ,june #bjth1 the top half-inch of soil was hotter than the air3 the mercury in the thermometer rose directly it was put into the soil4 ,there is nothing very unusual about this2 if you touch a piece of iron lying on the soil you find it hotter than the air4 ,lower down the soil had the same temperature as the air1 and still lower it was cooler#a4 ,the sun's heat travels so slowly into the soil in summer that months pass before it gets far down1 but then1 as it takes so long to get in1 it also takes a long time to get out1 and it takes still longer to get either in or out if there is a mulch or if grass is growing4 ,during the early winter you may notice that the first fall of snow soon melts on the arable land but remains longer on the grass2 towards the end of the winter1 however1 the reverse happens and the snow melts first on the grass4 ,there is no difficulty in explaining this4 ,the arable land is1 as we have seen1 warmer in autumn and early winter than grass land1 #ic and so it melts the snow more rapidly4 ,but during winter the grass land loses its heat more slowly1 and therefore it is warmer at the end of the winter than the arable land1 hence the snow melts more quickly4 ,in ,chap4 ,v4 it was pointed out that dark coloured soils rich in humus are greatly favoured by gardeners and farmers4 ,the value of humus can easily be shown3 take a sample of soil from a garden that has for a long time been well manured and another from a field close by--next to it if you can--and find the amounts of moisture present4 ,two soils at ,rothamsted gave the following results3-- ,date ,april #fth ,may #fth ,july #fth ,oct4 #bhth ,moisture in dark soil rich in humus #bj4j #ah4j #bj4g #bc4c ,moisture in lighter soil poor in humus #ac4a #aa4i #ab4j #ag4e ,humus1 therefore1 keeps the water in the soil and saves it from being lost4 ,another beneficial effect of hoeing is to keep down weeds4 ,weeds overcrowd the plant1 shut out light1 take food and water1 and occupy space4 ,few plants can compete against weeds1 some fail very badly in the struggle4 ,sow two rows of maize two yards apart2 keep one well hoed for a yard on each side and leave the other alone to struggle with the weeds that will grow4 ,fig4 #dd shows the result of this experiment at ,st ,george's ,school4 ,at ,rothamsted a piece of wheat was left unharvested in #ahhb1 and the plot has not been touched since2 the wheat was allowed to shed its seed #id and to grow up without any attention4 ,weeds flourished1 but the wheat did not2 the next year there was but little wheat1 and by #ahhf only a few plants could be seen1 so stunted that one would hardly recognise them4 ,the ground still remains untouched1 and is now the dense thicket seen in ,fig4 #de4 ,most of our land would become like this if it were neglected for a few years4 ,illustration3 ,fig4 #dd a4 ,the hoed plot1 no weeds4 ,maize cannot compete successfully against weeds #ie ,farmers occasionally leave their ground without a crop for a whole year and cultivate it as often as they can to kill the weeds4 ,this practice is called fallowing1 and is very ancient2 it is much less common now that crops like mangolds and swedes are grown1 which can1 if necessary1 be hoed all the summer4 ,illustration3 ,fig4 #dd b4 ,untouched plot1 many weeds ,we have already seen 7p4 #fi7 that ordinary cultivated plants will not live in a water-logged soil4 #if ,wherever there is an excess of water it must be removed before satisfactory results can be obtained4 ,fig4 #df shows a field of wheat in ,may where the crop is all but killed and only certain weeds survive on a patch of undrained land that lay wet all the winter4 ,draining land is difficult and somewhat expensive2 trenches are first cut to a proper depth1 and drain pipes are laid on the bottom1 taking care that there is a gentle slope all the way to the ditch4 ,the rain soaks into the soil and gets into the pipes1 for they are not joined together like gas or water pipes1 but left with little spaces in between2 it then runs out into the ditch4 ,usually only clay soils need drainage1 but occasionally sandy soils do also 7see pp4 #cj1 #ajf74 ,a great deal of drainage was carried out in ,england between #ahdj and #ahfj1 and it led to a marked improvement in agriculture and in country life generally4 ,there is1 however1 a great deal that wants doing now4 ,illustration3 ,fig4 #de4 ,a plot of wheat left untouched since #ahhb at ,rothamsted has now become a dense thicket ,the addition of chalk or lime to soil was found in ,chap4 ,,iii4 to improve it very much by making it less sticky and less impervious to air and water4 ,chalk or lime does more than this4 ,it puts out of action certain injurious substances or acids that may be formed1 and thus makes the conditions more favourable for plants and for the useful micro-organisms2 farmers and gardeners express this by saying that it sweetens the soil4 ,a ,united ,states proverb runs3 ,a lime country is a rich country4 ,very many soils in ,england are improved by adding lime or chalk4 ,there are considerable areas in the south-eastern and eastern counties where the soil is very chalky2 here you find a wonderfully rich assortment of flowers and shrubs4 ,where there is too much chalk the soil is not fertile1 because it lets water #ih through too easily1 as was shown on p4 #bf3 but for this very reason it is admirable for residential purposes4 ,there are some exceptions to the rule that plants need lime4 ,some plants will not tolerate it at all2 such are rhododendrons1 azaleas1 foxgloves1 spurrey1 and broom2 wherever you see these growing you may be sure that lime is absent4 ,lime really differs from chalk1 but changes into it so quickly in the soil that the action of both is almost1 though not quite1 the same4 ,illustration3 ,fig4 #df4 ,a wheat field in ,may4 ,the large patch in the centre where the crop is doing badly lay under water for much of the winter because of the bad drainage ,,summary4 ,the various things we have learnt in this ,chapter are3-- ,autumn and winter cultivation are needed to loosen the soil so that rain can soak in and not lie about in pools1 and also to facilitate working in spring4 ,the soil has to be broken down very finely and made rather dry for a seed bed4 ,the seed has to be rolled in and then left entirely alone4 ,as soon as the little plants are up the soil must be hoed1 and the more often this is done the better4 ,hoeing keeps the soil cool and moist in hot weather1 the loose layer acting like a mulch of straw4 ,anything else that shields the soil from the sun or the wind has the same action but is not so effective as the mulch4 ,further1 hoeing keeps down weeds1 which successfully compete against almost any cultivated plants4 ,humus also prevents the loss of moisture from soils4 ,drainage may be necessary to remove excess of water4 ,liming or chalking the soil is beneficial1 not only because of the improvements mentioned in ,chap4 ,,iii41 but also because certain injurious substances are thereby removed4 ,there are1 however1 some plants that will not tolerate lime4 #a ,at great depths below the surface the temperature rises again from quite another cause4 #ajj ,,chapter ,x ,,the ,,soil ,,and ,,the ,,countryside ,in this chapter we want to put together much of what we have learned about the different kinds of soil1 so that as we go about the country we may know what to look for on a clay soil1 a sandy soil1 and so on4 ,we have seen that clay holds water and is very wet and sticky in winter1 while in summer it becomes hard and dry1 and is liable to crack badly4 ,it greets a' winter and girns a' summer1 as one of ,dr ,john ,brown's characters said of his soil4 ,clay soils are therefore hard to dig and expensive to cultivate3 the farmer calls them heavy and usually prefers to put them into grass because once the grass is up it lasts as long as it is wanted and never needs to be resown4 ,but in the days when we grew our own wheat1 before we imported it from the ,united ,states and other countries1 this clay land was widely cultivated for wheat and beans4 ,so long as wheat was #fj_/- to #ajj_/- a quarter it was a very profitable crop1 but1 when some forty years ago it fell to #dj_/- and then lower still1 the land either went out of cultivation like the derelict farms of ,essex1 or it was changed to grass land and used for cattle grazing4 ,great was the distress that followed2 some districts indeed were years in recovering4 ,but new methods came in3 the land near ,london was used for dairy #aja farming1 and elsewhere it was improved for grazing1 and the clay districts1 although completely changed1 are now more prosperous again4 ,many of the fields still show the ridges or lands in which1 when they grew wheat1 they were laid up to let the water run away1 and many of them keep their old names1 but these are the only relics of the old days4 ,the land is not1 and never was1 very valuable4 ,the roads are wide1 and on either side have wide waste strips cut up roughly by horse tracks1 cart ruts and ant hills4 ,bracken1 gorse1 rushes1 thistles and brambles grow there1 and you may find many fine blackberries in ,september4 ,the coarse ,aira grass is found with its leaves as rough as files4 ,the villages are often built round greens which serve as the village playground1 where the boys and young men now play cricket and football1 and their forefathers practised archery1 played quoits and other games4 ,on a few village greens the ,maypole can still be seen1 whilst the stocks in which offenders were placed are also left in some places4 ,the hedges are often high and straggling1 and there are numerous woods and plantations containing much oak4 ,some of the woods are very ancient and probably form part of the primeval forests that once largely covered ,england4 ,epping ,forest in ,essex1 the ,forest of ,blean and the ,king's ,wood in ,kent1 have probably never been cultivated land4 ,in the days when ships were made of oak these woods and hedges were very valuable1 but now they are of little use as sources of timber4 ,instead they are valued for quite another reason3 they afford shelter for foxes and for game birds4 ,the clay districts are and always have been famous for fox hunting2 the ,pytchley1 ,quorn1 ,belvoir1 #ajb and other celebrated packs have their homes in the broad1 clay1 grassy vales of the ,midlands4 ,the vale of ,blackmoor and other clay regions are equally famous4 ,the plantations and hedgerows are fine places for primroses and foxgloves1 while in the pastures1 and especially the poor pastures1 are found the ox-eyed daisy and quaking grass1 that make such fine nosegays1 as well as that sure sign of poverty1 the yellow rattle4 ,but many of these poor pastures have been improved by draining1 liming1 and the use of suitable manures4 ,although the roads are better than they were 7see p4 #cj7 they are still often bad and lie wet for weeks together in winter1 especially where the hedges are high4 ,numerous brick and tile yards may be found and iron ore is not uncommon2 in some places it is worked now1 in others it is no longer worked and nothing remains of the lost industry save only a few names of fields1 of ponds1 or of cottages4 ,illustration3 ,fig4 #dg4 ,highly cultivated sand in ,kent4 ,gooseberries are growing in the foreground1 vegetables behind1 and hops in background ,a sandy soil is in so many ways the opposite of a clay soil that we shall expect to find corresponding differences in the look of the country4 ,a sandy soil does not hold water3 it may get water up from the subsoil to supply the plant 7see p4 #ff71 or1 if it happens to lie in a basin of clay1 it may even be very wet3 otherwise it is likely to be too dry for ordinary plants4 ,we may therefore look out for two sorts of sand country1 the one cultivated because there is enough water for the crops1 and the other not cultivated because the water is lacking4 ,these can readily be found4 ,we will study the cultivated sands first4 ,as sand is not good plant food 7p4 #dc7 these soils want a lot of manure1 and so are not good for ordinary farmers4 ,but they are very easy to cultivate--for which reason they #ajd are called light soils--and can be dug at any time2 seeds can be sown early1 and early crops can be got4 ,consequently these soils are very useful for men doing special work like fattening winter and spring sheep1 or producing special crops like fruit or potatoes1 and for market gardeners who grow all sorts of vegetables1 carrots1 parsnips1 potatoes1 peas1 and so on4 ,fig4 #dg is a view of a highly cultivated sandy region in ,kent showing gooseberries in the foreground1 vegetables behind1 and a hop garden behind that again4 ,illustration3 ,fig4 #dh4 ,a ,surrey heath ,the uncultivated sands are sometimes not really so very different1 and some of them1 perhaps many of them1 might be improved or reclaimed and made to grow these special crops if it were worth while4 ,but they always require special treatment and therefore they have been left alone4 ,in days of old our ancestors disliked them very much2 villanous1 rascally heaths ,cobbett always called them4 ,there were practically no villages and few cottages1 because the land was too barren to produce enough food2 the few dwellers on the heath1 or the heathen1 were so ignorant and benighted that the name came to stand generally for all such people and has remained in our language long after its original meaning was lost4 ,as there were so few inhabitants the heaths used to be great places for robbers1 highwaymen1 and evil-doers generally2 ,gad's ,hill on the ,watling ,st4 between ,rochester and ,gravesend1 ,finchley ,common1 ,hounslow ,heath and others equally dreaded by travellers of the seventeenth and eighteenth centuries1 were barren sandy tracts4 ,but in our time we no longer need to dread them2 we can enjoy the infinite charm of the breezy1 open country with its brown vegetation1 the pink blossom of the bell-shaped heath and the lilac blossom of the #ajf heather1 the splashes of yellow from the ragwort or the gorse and the dark pine and larch plantations4 ,in the spring the young shoots of bracken lend a beautiful light green colour to the scene1 while in the autumn the faded growth covers it all with a rich brown4 ,people now like to live amid such surroundings1 and so these heaths1 that have been untouched for so long and are part of the original primeval ,england as it was in the days of the ,britons1 are becoming dotted with red bricked and red tiled villas1 and are fast losing their ancient character4 ,the heaths are not everywhere dry2 there are numerous clay basins where the sand lies wet1 where peat forms 7see p4 #cg71 and where marsh plants like the bog asphodel1 sundew1 or cotton grass can be found4 ,in walking over a heath you soon learn to find these wet places by the colour of the grass and the absence of heather4 ,in some places there is a good deal of wood1 especially pines1 larches1 and silver birches3 all these are very common on the ,surrey sands1 willows also grow in the damp places4 ,fig4 #dh shows a ,surrey heath--,blackheath--with heather1 gorse and bracken2 with pine-woods in the distance and everywhere some bare patches of sand4 ,much of the ,new ,forest is on the sand1 as also is ,bournemouth1 famous for its fine pine woods4 ,fig4 #di is a view of such woods on ,wimbledon common4 ,but elsewhere there is no wood3 the peasants burn the turf1 and so you find their cottages have huge fireplaces3 instead of fences round their gardens or round the plantations there are walls made of turf4 ,such are the ,dorchester heaths so finely described by ,hardy in ,the ,return of the ,native and other novels4 ,other sands1 however1 are covered with grass and not with heather1 and many of these have a special value #ajh for golf links1 especially some of the dry1 invigorating sands by the seaside4 ,the famous links at ,st ,andrews1 and at ,littlestone1 are examples4 ,illustration3 ,fig4 #di4 ,woodland and heather on light sandy soil1 ,wimbledon ,common ,in between the fertile and the barren sands come a number that are cultivated without being very good4 ,they are much like the others1 carrying a vegetation that is usually of the narrow leaved type 7p4 #gb71 and not very dense4 ,on the road sides you see broom1 heather1 heath1 harebells1 along with gorse and bracken with milkwort nestling underneath3 crested dog's tail and sheep's fescue are common grasses1 while spurrey1 knotwood1 corn marigold1 are a few of the numerous weeds in the arable fields4 ,gardens are easily dug1 but it is best to put into them only those plants that1 like the native vegetation1 can withstand drought3 vegetable gardens must be well manured and well limed4 ,fig4 #ej shows some of this kind of country in ,surrey1 the barley field is surrounded by wood and very poor grass on the higher slopes4 ,illustration3 ,fig4 #ej4 ,poor sandy soil in ,surrey1 partly cultivated but mainly wood and waste ,it is easy to travel in a sand country because the roads dry very quickly after rain1 although they may be dusty in summer4 ,sometimes the lanes are sunk rather deeply in the soft sand1 forming very pretty banks on either side4 ,loams1 as we have seen 7p4 #b71 lie in between sands and clays3 they are neither very wet nor very dry3 not too heavy nor yet too light3 they are very well suited to our ordinary farm crops1 and they form by far the best soils for general farming2 wheat1 oats1 barley1 sheep1 cattle1 milk1 fruit and vegetables can all be produced3 indeed the farmer on a good loam is in the fortunate position of being able to produce almost anything he finds most profitable4 ,in a loam district that does not #aaj lie too high the land is generally all taken up1 even the roads are narrow and there are few commons4 ,the hedges are straight and cut short1 the farm houses and buildings are well kept1 and there is a general air of prosperity all round4 ,good elms grow and almost any tree that is planted will succeed4 ,loams shade off on one side into sand2 the very fertile sands already described might quite truly be called sandy loams4 ,on the other side they shade off into clays2 the heavy loams used to be splendid wheat soils1 but are now1 like clays1 often of little value4 ,but they form pleasant1 undulating country1 nicely wooded1 and dotted over with thatched cottages2 the fields are less wet and the roads are rather better than on the clays4 ,when properly managed they make excellent grass land4 ,chalky soils stand out quite sharply from all others3 their white colour1 their lime kilns now often disused1 their noble beech trees1 and1 above all1 the great variety of flowering plants enable the traveller at once to know that he is on the chalk4 ,many plants like chalk and these may be found in abundance1 but some1 such as foxgloves1 heather1 broom or rhododendrons cannot tolerate it at all1 and so they will not grow4 ,chalk1 like sand1 is dry1 and the roads can be traversed very soon after rain4 ,they are not very good1 however2 often they are only mended with flints1 which occur in the chalk and are therefore easily obtainable1 and the sharp fragments play sad havoc with bicycle tyres4 ,the bye roads and lanes are often narrow1 winding1 and worn deep especially at the foot of the hills1 so that the banks get a fair amount of moisture and carry a dense vegetation4 ,among the profusion of flowers you can find scabious1 the bedstraws1 vetches1 ragwort1 #aaa figwort1 and many a plant rare in other places1 like the wild orchids2 while the cornfields are often yellow with charlock4 ,in the hedgerows are hazels1 guelder roses1 maples1 dogwood1 all intwined with long trails of bryony and traveller's joy4 ,in the autumn the traveller's joy produces the long1 hairy tufts that have earned for it the name of old man's beard1 while the guelder roses bear clusters of red berries4 ,the great variety of flowers attracts a corresponding variety of butterflies1 moths and other insects2 there are also numbers of birds and rabbits--indeed a chalk country teems with life in spite of the bare look of the ,downs4 ,the roads running at the foot of the chalk ,downs and connecting the villages1 and farmhouses built there for the good water supply1 are particularly rich in plants because they sometimes cut into the chalk and sometimes into the neighbouring clay1 sand or rock4 ,now and then a spring bursts out and a little stream takes its rise3 if you follow it you will generally find watercress cultivated somewhere4 ,besides the beech trees you also find ash1 sycamore1 maples1 and1 in the church yards1 some venerable yews4 ,usually the chalk districts were inhabited very early3 they are dry and healthy1 the land can be cultivated and the heights command extensive views over the country1 so that approaching enemies could easily be seen4 ,on the chalk downs and plains are found many remains of tribes that lived there in the remote ages of the past1 whose very names are now lost4 ,strange weapons and ornaments are sometimes dug up in the camps where they lived and worked2 the barrows can be seen in which they were buried1 and the temples in which they worshipped2 ,stonehenge itself1 the best known of all these1 lies on the chalk4 #aab ,several of the camps still keep the name the ancient ,britons gave them--the ,mai-dun1 the encampment on the hill1 changed in the course of years to ,maiden1 as in ,maiden ,hill1 near ,dorchester1 in ,dorset1 ,maiden ,bower1 near ,dunstable1 and so on4 ,some of their roads are still in use to this day1 the ,icknield ,way 7the way of the ,iceni1 a ,belgic tribe71 the ,pilgrim's ,way of the southern counties and others4 ,even the present villages go back to very ancient times1 and the churches are often seven or eight hundred years old4 ,in places the land is too steep or too elevated to be cultivated1 and so it is left as pasture for the sheep or sheep walk2 where cultivation is possible the fields are large and without hedges1 like those shown in ,fig4 #ea2 during autumn1 winter and spring there are many sheep about1 penned or folded on the arable land1 eating the crops of swedes1 turnips1 rape1 vetches or mustard grown for them1 or grazing on the aftermath of sainfoin or grass and clover4 ,so important are sheep in chalk districts that the whole scheme of farming is often based on their requirements1 but corn is also a valuable crop1 and1 especially in dry districts1 barley1 so that chalk soils are often spoken of as sheep and barley soils4 ,although the pastures are very healthy there is not generally much food or keep for the animals during the summer because of the dryness4 ,illustration3 ,fig4 #ea4 ,open chalk cultivated country1 ,isle of ,thanet ,the black soil of the fen districts and elsewhere is widely different from any of the preceding4 ,it contains1 as its colour shows1 a large quantity of combustible material 7,chap4 ,v471 which has a great power of holding water4 ,these fens are therefore very wet2 until they were drained they were desolate wastes3 you may #aad read in ,kingsley's ,hereward the ,wake what they used to be like in old days1 and even as late as #affb ,dugdale writes that here no element is good4 ,the air cloudy1 gross and full of rotten harrs#a2 water putrid and muddy1 yea1 full of loathsome vermin2 the earth spongy and boggy2 and the fire noisome by the stink of smoking hassocks#b4 ,but during the ,stuart period wide ditches or drains were dug1 into which the water could flow and be pumped into rivers4 ,this reclamation has been continued to the present time1 and the black soils as well as the others in the ,fen districts can be made very productive4 ,we have seen that a change in the soil produces a change in the plants that grow on it4 ,the flora 7i4e4 the collection of plants7 of a clay soil is quite different from that of a sandy soil1 and both are different from that of a chalk or of a fen soil4 ,in like manner draining a meadow or manuring it alters its flora3 some of the plants disappear and new ones come in4 ,even an operation like mowing a lawn1 if carried on sufficiently regularly1 causes a change4 ,in all these cases the plants favoured by the new conditions are enabled to grow rather better than those that are less favoured2 thus in the regularly mown lawn the short growing grasses have an advantage over those like brome that grow taller1 and so crowd them out4 ,when land is drained those plants that like a great quantity of water no longer do quite so well as before1 while those that cannot put up with much water now have a better chance4 ,in the natural state there is a great deal of competition among #aae plants1 and only those survive that are adapted to their surroundings4 ,you should remember this on your rambles and when you see a plant growing wild you should think of it as one that has succeeded in the competition and try to find out why it has been enabled to do so4 #a ,harr is an old word meaning sea-fog4 #b ,hassock is the name given to coarse grass which forms part of the turf burnt in the cottages4 #aaf ,,chapter ,,xi ,,how ,,soil ,,has ,,been ,,made ,apparatus required4 ,the apparatus in ,fig4 #ed4 ,the under surface1 of the lips of the beakers should be vaselined to prevent the water trickling down the sides4 ,it is not uncommon to find cliffs or crags in inland places1 but they usually show one very striking difference from seaside cliffs4 ,the seaside cliffs may be nearly vertical1 but the inland cliffs are not1 excepting for a little way at the top2 lower down a heap of stones and soil lies piled against the face of the cliff and makes a slope up which you can climb4 ,if you look at the cliff you can find loose fragments of it split off either by the action of freezing water 7p4 #hc7 or by other causes ready to roll down if sufficiently disturbed4 ,so long has this been going on that a pile has by now accumulated1 and has been covered with plants growing on the soil of the heap4 ,our interest centres in this soil2 no one has carried it there2 it must have been made from the rock fragments4 ,when you get an opportunity of studying such a heap1 do so carefully2 you can then see how1 starting from a solid rock1 soil has been formed4 ,this breaking down of the rock is called weathering4 ,illustration3 ,fig4 #eb4 ,cliffs at the seaside1 ,manorbier1 ,pembrokeshire ,the same change has gone on at the top of the cliff4 ,fragments have split off and the rock has broken #aah down into soil which stops where it is unless the rain can wash it away4 ,if there are no cliffs where you live you can see the same kind of action in the banks of the lanes1 in a disused quarry1 gravel pit or clay pit4 ,wherever a vertical cutting has been made this downward rolling begins and a heap quickly forms1 making the vertical cut into a slope4 ,plants soon begin to grow1 and before long it is clear that soil has been made out of the fragments that have rolled down4 ,this process is known as soil formation1 but there is another always going on that we must now study4 ,the heap does not invariably lie at the foot of the cliff4 ,if there is a stream1 river1 or sea at the foot the fragments may be carried away as fast as they roll down3 the differences shown in ,figs4 #eb and #ec between a cliff at the seaside and a cliff inland arise simply in this way4 ,in inland districts great valleys are in course of time carved out1 and at the seaside large areas of land have been washed away4 ,what becomes of the fragments thus carried away by the water8 ,the best way of answering the question would be to explore one of these mountain streams and follow it to the sea1 but we can learn a good deal by a few experiments that can be made in the classroom4 ,we want to make a model stream and see what happens to little fragments of soil that fall into it4 ,illustration3 ,fig4 #ec4 ,inland cliff4 ,salisbury ,crags1 ,arthur's ,seat1 ,edinburgh ,fix up the apparatus shown in ,fig4 #ed4 ,the small beaker ,a is to represent the narrow mountain stream1 the larger one ,b stands for the wide river1 and the glass jar ,c for the mouth of the river or the sea4 ,run water through them2 notice that it runs quickly through ,a1 slowly through ,b1 and still more slowly through ,c3 we want it to do this1 because the stream flows quickly and the river slowly4 #abj ,now put some soil into ,a4 ,at once the soil is stirred up1 the water becomes muddy1 and the muddy liquid flows into ,b4 ,but very soon a change sets in1 the liquid in ,a becomes clear1 and only the grit and stones are left in the bottom3 all the mud--the clay and the silt--is washed into ,b4 ,there it stops for a long time1 and some of it will never wash out4 ,the liquid flowing into ,c is clearer than that flowing into ,b4 ,if you keep on putting fresh portions of soil into ,a you can keep ,b always muddy1 although ,a is usually clear4 ,at the end of the experiment look at the sediment in each beaker3 in ,a it is clear and gritty1 in ,b it is muddy4 ,if you can get hold of some sea water put some of the liquid from ,c into it3 very soon this liquid clears and a deposit falls to the bottom1 the sea water thus acting like the lime water on p4 #bj4 ,illustration3 ,fig4 #ed4 ,model of a stream4 ,in ,a1 where the stream flows quickly1 the water is clear and the sediment free from mud4 ,in ,b1 where it flows slowly1 the water is turbid and the sediment muddy #aba ,the experiment shows us that the fine material washed away by a quickly flowing stream is partly deposited when the river becomes wider and the current slower1 and a good deal more is deposited by the action of the salt water when the river flows into the sea4 ,the rock that crumbles away inland is spread out on the bed of the river or at its mouth4 ,illustration3 ,fig4 #ef4 ,the two sides of the river at the bend ,the river ,stour at ,wye showed all these things so clearly that ,i will describe it2 you must then compare it with a river that you know1 and see how far the same features occur4 ,at the bridge the stream was shallow and flowed quickly3 the bottom was gritty and pebbly1 free from mud1 and formed a safe place for paddling4 ,before the bridge was built there had been #abb a ford here4 ,but further away1 either up or down1 the stream was deeper and wider1 flowed more slowly1 had a muddy bottom1 and so was not good for paddling4 ,at one place about a mile away some one had widened out the river to form a lake1 but this made the stream flow so slowly 7as it was now so much wider7 that the silt and clay deposited and the lake became silted up1 i4e4 it became so shallow that it was little more than a lake of mud4 ,the same facts were brought out at the bend of the river4 ,on its convex side1 ,fig4 #ee1 the water has rather further to go in getting round the bend than on its concave side ,b1 it therefore flows more quickly1 and carries away the soil of the bank and mud from the bottom4 ,but on its concave aide where it flows more slowly it deposits material4 ,there is at the bend a marked difference in depth at the two sides4 ,on its convex side the stream is rapid and deep1 and scours away the bank2 on its concave side it is slower1 shallower1 and tends to become silted up4 ,thus the bend becomes more and more pronounced unless the bank round ,a is protected 7the other bank of course needs no protection7 and the whole river winds about just as you see in ,fig4 #ef1 and is perpetually changing its course1 carrying away material from one place1 mixing it up with material washed from somewhere else1 and then deposits it at a bend or in a pool where it first becomes a mud flat and then dry land4 ,some1 however1 is carried out to sea4 ,we need not follow the ,stour to the sea2 reference to an atlas will show what happens to other rivers4 ,some of the clay and silt they carry down is deposited at their mouths1 and becomes a bar1 gives rise to shoals and banks1 or forms a delta4 ,the rest is carried away and deposited on the floor of the sea4 #abd ,material washed away by the sea from the coast is either deposited on other parts of the coast1 or is carried out and laid on the floor of the sea4 ,thus a thick deposit is accumulating1 and if the sea were to become dry this deposit would be soil4 ,this has actually happened in past ages4 ,the land we live on1 now dry land1 has had a most wonderful history2 it has more than once lain at the bottom of the sea and has been covered with a thick layer of sediment carried from other places4 ,then the sea became dry land and the sediment became pressed into rock1 which formed new soil1 but it at once began to get washed away by streams and rivers into new seas1 and gave rise to new sediments on the floor of these seas4 ,and so the rock particles have for untold ages been going this perpetual round3 they become soil2 they are carried away by the rivers1 in time they reach the sea2 they lie at the bottom of the sea while the sediment gradually piles up3 then the sea becomes dry land and the sediments are pressed into rocks again4 ,the eating away of the land by water is still going on3 it is estimated that the whole of the ,thames valley is being lowered at the rate of about one inch in eight hundred years4 ,this seems very slow1 but eight hundred years is only a short time in geology1 the science that deals with these changes4 ,illustration3 ,fig4 #ef4 ,the winding river ,stour4 ,the river winds from the right to the left of the picture1 then back again1 and then once more to the left1 passing under the white bridge and in front of the barn4 ,water does more than merely push the rock particles along4 ,it dissolves some of them1 and in this way helps to break up the rock4 ,spring water always contains dissolved matter1 derived from the rocks1 some of which comes out as fur in the kettles when the water is boiled4 ,rocks are also broken up by other agents4 ,there is nearly always some lichen living on the rock1 and if you #abe peel it off you can see that it has eaten away some of the rock4 ,when the lichen dies it may change into food for other plants4 ,we have learnt these things about soil formation4 ,first of all the rocks break up into fragments through the splitting action of freezing water1 the dissolving action of liquid water1 and other causes4 ,this process goes on till the fragments are very small like soil particles4 ,then plants begin to grow1 and as they die and decay they give rise to the black humus that we have seen is so valuable a part of the soil 7p4 #ea74 ,this is how very many of our soils have been made4 ,but the action of water does not stop at breaking the rock up into soil2 it goes further and carries the particles away to the lower parts of the river bed1 or to the estuary1 to form a delta1 and mud flats that may be reclaimed1 like ,romney ,marsh in ,england and many parts of ,holland have been4 ,many of our present soils have been formed in this way4 ,finally the particles may be carried right away to sea and spread out on the bottom to lie there for many ages1 but they may become dry land again and once more be soil4 ,one thing more we learnt from the river ,stour4 ,why did it flow quickly at the bridge and slowly elsewhere8 ,we knew that the soil round the bridge was gravelly1 whilst up and down the stream it was clayey4 ,the river had not been able to make so wide or so deep a bed through the gravel as it had through the clay1 and it could therefore be forded here4 ,we knew also that there was a gravel pit at the next village on the river1 where also there was a bridge and had been a ford1 and so we were able to make a rough map like ,fig4 #eg1 showing that fords had occurred at the gravel #abf patches1 but not at the clay places4 ,now it was obvious that an inn1 a blacksmith's forge1 and a few shops and cottages would soon spring up round the ford1 especially as the gravel patch was better to live on than the clay round about1 and so we readily understood why our village had been built where it was and not a mile up or down the stream4 ,almost any river will show the same things3 on the ,lea near ,harpenden we found the river flowed quickly at the ford 7,fig4 #eh71 where there was a hard1 stony bottom and no mud3 whilst above and below the ford the bottom was muddy and the stream flowed more slowly4 ,at the ford there is as usual a small village4 ,the ,thames furnishes other examples3 below ,oxford there are numerous rocky or gravelly patches where fords were possible1 and where villages therefore grew up4 ,above ,oxford1 however1 the possibilities of fording were fewer1 because the soil is clay and there is less rock2 the roads and therefore the villages grew up away from the river4 ,illustration3 ,fig #eg4 ,sketch map showing why ,godmersham and ,wye arose where they did on the ,stour4 ,at ,a1 the gravel patch1 the river has a hard bed and can be forded4 ,a village therefore grew up here4 ,at ,b1 the clay part1 the river has a soft bed and cannot be forded4 ,the land is wet in winter1 and the banks of the stream may be washed away4 ,it is therefore not a good site for a village ,illustration3 ,fig4 #eh4 ,ford and ,coldharbour1 near ,harpenden #abh ,,appendix ,the teacher is advised to procure1 both for his own information and in order to read passages to the scholars3 ,gilbert ,white1 ,natural ,history of ,selborne4 ,charles ,darwin1 ,earthworms and ,vegetable ,mould 7,murray74 ,a4 ,d4 ,hall1 ,the ,soil 7,murray74 ,mr ,hugh ,richardson has supplied me with the following list of questions1 through many of which his scholars at ,bootham ,school1 ,york1 have worked4 ,they are inserted here to afford hints to other teachers and to show how the lessons may be varied4 ,they should also prove useful for revising and testing the scholars' knowledge4 #a4 ,collect samples of the different soils in your neighbourhood--garden soil1 soil from a ploughed field1 from a mole-hill in a pasture field1 leaf mould from a wood1 etc4 ,collect also samples of the sub-soils1 sand1 gravel1 clay1 peat4 #b4 ,supplement your collection by purchasing from a gardener's shop some mixed potting soil and also the separate ingredients used to form such a mixture--silver sand1 leaf mould1 peat4 #c4 ,how many different sorts of peat can you get samples of8 ,peat mould1 peat moss litter1 sphagnum moss1 turf for burning1 dry moor peat8 #d4 ,find for what different purposes sand is in use1 such as mortar making1 iron founding1 scouring1 bird cages1 and obtain samples of each kind4 #abi ,analysis of ,garden ,soil4 ,about a handful of soil will be required by each pupil4 #e4 ,describe the appearance of the soil4 ,is it fine or in lumps8 ,does it seem damp or dry8 ,can you see the separate particles of mineral matter8 ,how large are these8 ,is there any evidence of vegetable matter in the soil8 #f4 ,put some of the soil in an evaporating basin and over this place a dry filtering funnel4 ,warm the basin gently4 ,is any moisture given off8 #g4 ,dry some of the soil at a temperature not greater than that of boiling water1 e4g4 by spreading it out on a biscuit tin lid1 and laying this on a radiator4 ,how have the appearance and properties of the soil been changed by drying8 #h4 ,crumble some of the dried soil as finely as you can with your fingers4 ,then sift it through a sheet of clean wire gauze4 ,what fraction of the soil is fine enough to go through the gauze8 ,describe the portion which will not pass through the gauze4 ,count the number of wires per linear inch in the gauze4 #i4 ,mix some of the soil with water in a flask4 ,let it stand4 ,how long does it take before the water becomes quite clear again8 #aj4 ,mix some more soil with water4 ,let it settle for #cj seconds only4 ,pour off the muddy water into a tall glass cylinder4 ,add more water to the remaining soil1 and pour off a second portion of muddy water1 adding it to the first1 and so on until all the fine mud is removed from the soil4 ,allow this muddy water ample time to settle4 #aa4 ,when the fine mud has settled pour off the bulk of the water2 stir up the mud with the rest of the water2 transfer it to an evaporating basin1 and evaporate to dryness4 #ab4 ,does this dried mud consist of very tiny grains of sand or of some material different from sand8 ,can you find out with a microscope8 #ac4 ,if the mud consists of real clay and not of sand it should be possible to burn it into brick4 ,moisten the dried mud again4 ,roll it if you can into a round clay marble4 ,leave this to dry slowly for a day4 ,then bake it either in a chemical laboratory furnace or in an ordinary fire4 #ad4 ,return to the soil used in ,question #aj1 from which only the fine mud has been washed away4 ,pour more water on to it1 shake it #acj well1 and pour off all the suspended matter without allowing it more than #e seconds to settle4 ,repeat the process4 ,collect and dry the poured off material as before4 ,what is the material this time1 sand or clay8 #ae4 ,wash the remaining portion of the soil in ,question #ad clean from all matter which does not settle promptly4 ,are there any pebbles left8 ,if so1 how large are they1 and of what kind of stone8 #af4 ,take a fresh sample of the soil4 ,mix it with distilled water in a flask4 ,boil the mixture4 ,allow it to settle4 ,filter4 ,divide the filtrate into two portions4 ,evaporate both1 the larger portion in an evaporating basin over wire gauze1 the smaller portion in a watch glass heated by steam4 ,is any residue left after heating to dryness8 #ag4 ,take a fresh sample of soil4 ,spread it on a clean sand bath and heat strongly with a ,bunsen flame4 ,does any portion of the soil burn8 ,is there any change in its appearance after heating8 #ah4 ,to a fresh sample of soil add some hydrochloric acid4 ,is there any effervescence8 ,if so1 what conclusions do you draw8 #ai4 ,make a solution of soil in distilled water1 and filter as before4 ,is this solution acid1 alkaline or neutral8 ,are you quite certain of your result8 ,did you test the distilled water with litmus paper8 ,and are you sure that your litmus does not contain excess of free acid or free alkali8 ,peat4 #bj4 ,examine different varieties of peat collected 7see ,question #b7 and describe the appearance of each4 #ba4 ,burn a fragment of each kind of peat on wire gauze4 ,what do you notice8 #bb4 ,boil some peat with distilled water and filter the solution4 ,what colour is it8 ,can you tell whether it is acid1 neutral or alkaline8 ,evaporate some of the solution to dryness4 ,out-of-doors4 #bc4 ,describe the appearance of the soil in the flower beds 7a7 during hard frost1 7b7 in the thaw which follows a hard frost1 7c7 after an ,april shower1 7d7 in drought at the end of summer1 7e7 in damp ,october weather when the leaves are beginning to fall4 #bd4 ,is the soil equally friable at different times of the year8 #aca #be4 ,in what way do dead leaves get carried into the soil8 #bf4 ,can you find the worm holes in a garden lawn8 in a garden path8 #bg4 ,take a flower bed or grass plot of small but known area 7say #c yards by #b yards7 and a watering can of known capacity 7say #c gallons74 ,find how much water must be added to the soil before some of the water will remain on the surface4 ,what has been the capacity of the soil in gallons per square yard8 #bh4 ,take two thermometers4 ,lay one on the soil1 the other with its bulb #c inches deep in the soil4 ,compare their temperatures at morning1 noon and night4 #bi4 ,find from the #be-;inch ,ordnance map the reference numbers of the fields near your school4 ,make a list of the fields1 showing for what crop or purpose each field is being used4 #acb ,,index ,acid waters1 #dj ,air in soil1 #af1 #gj1 #ie ,bars in estuaries1 #abb ,black soils1 #cf ,blowing sands1 #bb ,bricks1 #aj1 #af-ah ,chalk1 #bf1 #if ,chalk soils1 #aaj-aab ,clay1 #f1 #i-ba ,clay soils1 #ge1 #ajj-ajb ,cliffs1 #aaf-aai ,darwin's experiments1 #aa1 #ef ,deltas1 #abb ,drainage1 #ai1 #if ,dwellers in the soil1 #ec-fc ,earthworms1 #ed-ef ,error of experiment1 #dh ,fallow1 #ad1 #ie ,fens1 #aab ,flora1 #aad ,fords1 #abf ,frost1 action of1 on soil1 #hc ,grassland1 #ge ,grit1 #f ,hales's experiment1 #gc ,heaths1 #ajd ,heavy soils1 #ajj ,hoeing1 #hf-ic ,humus1 #cf1 #ea1 #ic1 #abe ,hypotheses1 #cf ,land slips1 #ab ,leaf mould1 #cc ,light soils1 #ajd ,lime1 action of1 on clay and soil1 #ai-ba1 #if-ih ,lime water1 #ai ,loams1 #b1 #fe1 #ajh ,marsh gas1 #dj ,micro-organisms1 #ef-fb ,moorland1 #hj ,mulch1 #hg1 #ij ,peat1 #cg-dj1 #acj ,peat bogs1 overflow of1 #ch ,perspiration of plants1 #gd ,plant food1 #da-eb1 #fb ,plant requirements1 #fd ,ploughing1 #hb ,pot experiments1 #da-eb1 #ed1 #fi1 #ga ,roads1 #cj-cb1 #aja-aab ,rolling the soil1 #hd ,sand1 #f1 #bb-cb1 #da ,sand dunes1 #bb ,sandy soils1 #fh-gb1 #ajb-ajh ,shrinkage of clay1 #aj ,silt1 #g ,soil sampler1 #hb1 #hh ,sowing seed1 #hd ,springs1 #bd-ca1 #aaa ,subsoil1 #b1 #d1 #db1 #dh-ea ,swelling of clay1 #aa ,swelling of peat1 #ch ,temperature of soil1 #hf-ic ,tilth1 #hf ,van ,helmont's experiment1 #df ,villages1 situation of1 #bd1 #cj1 #abf ,wastes1 #aja1 #ajd ,water content of soil1 #hh-ic ,water1 movement of in soils1 #fe-fh ,water supply and plant growth1 #fi-gd ,weathering1 #aaf ,weeds1 #id1 #ig ,woodland1 #hj1 #aja