1847. 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



siderable quantity of red marl, containing a large proportion of calcareous 

 and argillaceous matter, and this, when brouglit to the surface, made a most 

 excellent soil. The rich grazing lands of Devonshire and Cheshire, and 

 other parts of England, were constituted of this kind of soil. It was also 

 manageable from its ready drainage, and valuable from the salt obtained 

 from it. 



The next substance was lias, and then the whole series of oolites. Lias 

 consisted of thick beds of argillaceous matter, which was more extensively 

 3een in plains and valleys. It formed a very valuable soil, and might be 

 traced throughout England. Lias contained a good deal of calcareous mat- 

 ter, and was not far removed from the new red sandstone on the one side, 

 and the lower sands of the oolites on the other. The oolites were a large 

 elass, wliich supplied in their lower portions a great quantity of building 

 stone, quarried in the neighbourhood of Bath, near Oxford, at Ketton, in 

 Northamptonshire, and elsewhere. These rocUs were often overlaid by beds 

 of clay of considerable thickness, as in the fens of Lincolnshire and Cam- 

 bridgeshire ; and in their upper portion the oolites again contained a quan- 

 tity of hard and valuable building stones, as in Portland Island. 



Lastly, there were the cretaceous rocks, which included the dark red sands 

 of Bedfordshire, and the broad and extensive downs of Sussex and Wiltshire, 

 and extended through England to Yorkshire. 



Geological Science ui>j)liid to ike Mirlure of Soils, mid to Draining 

 for Agricultural Purjtoses. 

 Professor Ansteu prefaced his remarks, upon the ubove-raentioued 

 highly interesting topics, by some observations upou the forniuliou of soils 

 from certain rocks, which, in his previous lecture, he had hut just glanced 

 at; and, first, as to the ci-etaceous, or chalk formation, which extended 

 from the western coast of England, commeucing near Portland Island, in 

 Dorsetshire, and runuiiig in a north-east direction, through Buckingham- 

 shire and Bedfordshire, lo the east and south-eastern shores. The chalk 

 formation was divided into two kinds ; the most important of which, in 

 some respects, was that known as the lower green sand series. This sand, 

 in Bedfordshire, and some other places, was of a very dark red colour, 

 which, by itself, was liahle to be very barren; but, when mixed with 

 clay, it made a very rich soil, particularly if the clay coniaiued a propor- 

 tion of limestone. The lower green sand was generally underlaid by the 

 Kimmeridge clay, covered irp wiih the gault, which, in Cambridgeshire 

 and elsewhere, formed a stift' clay. la either case, the materials would 

 bear mixing with lire green sand, and generally produced rich and produc- 

 tive soils— this formation was, therefore valuable. The upper cretaceous 

 bcls contained cnrhonaie of linre in too pure a state to furnish of itself a 

 good agricultural soil. In this way, the chalk could not be considered as 

 affording of itself a rich soil ; but rather one which was capable of being 

 made so. It was, however, valuable as a grazing soil for sheep, producrng 

 a short line grass ; but the quantity of surface required for the support of 

 a small number of aniinals diminished its value in this respect very con- 

 siderably. 



He next referred to the tertiary beds, which, iu England, embraced only 

 a comparatively small series. The London clay formed the great mass of 

 the tertiary deposits: it was found principally in the neighbourhood of the 

 Thames, and in Hampshire. The Loudon clay was geuer-ally underlaid 

 by a more plastic clay, and covered with sand. This was particularly the 

 case at Uagshot Heath, in a large tract of country nearM'oking, traversed 

 by the South Eastern iiailway ; and those who had travelled upou that 

 line would have remarked that it passed for the most part through a poor 

 and somewhat sterile country ; though, where the clay was mixed with 

 pebbles and sand, it was capable of becoming looser in its texture, and of 

 being made a more available soil, and, indeed, a valuable oue, by means of 

 a great deal of manure. The tertiary beds, however, could not be con- 

 sidered naturally valuable for agriculture, although they were often made 

 so from local circumstances. The terliai-y deposits of Suffolk and Essex 

 ■were called crag, and consisted either of a shelly or marly sand, but gene- 

 rally shelly. Tliis was particularly capable of being made a good soil, 

 when mixed with the clajs near it. 



There were other beds which, as geologists, they were bound to con- 

 sider — namely, those which were known by the general name of gi-avel, 

 which was a mixture of pebbles and sand, and, being liable to accunitrlate 

 in every favourable locality, was met with everywhere ; it was, in fact, 

 the most abundant of the earth's superficial coatings. The circumstances 

 which induced it were exceedingly various, though mostly connected with 

 the changes elfected by running water. Where it had accumulated sud 

 denly,the finest sand would be found mixed with the coarsest pebbles ; in 

 other cases, it nrigltt contain a great deal of clay ; and iu others, silt. 

 These formed masses, which required always to be considered in regard to 

 their local relations. OSravel cunstrtuted not a had soil for agriculture, as 

 it was i-eadily drained ; but it depended on what was near it, or with it, 

 whether it could be made a good one. 



All the cir-cumstances connected with the formation and nature of soils 

 geologically must be taken into account when the agriculturalist studied 

 that most important subject, the improvement of the soil by admixtures of 

 other sorls. This was a question which required the most careful hand- 

 ling, as it was a dangerous thing to play with soils, and equally hazardous 

 to make speculative changes wtthout a good chemical knowledge. To 

 mix sods with advantage, it was indispensable to have a certain amount of 

 that knowledge, aud also an intimate acquaintance with many facts which 

 were purely geological. 



In the first place, it was important, if the soil at the surface was not 

 good, and it was sought to be improved by a mixture, to consider its geo- 

 logical relations, the circtrmstances under which it was presented, and the 

 way in which it was associated with the surrounding material. The ap- 

 pearance of the surface, the structure of the country, the way the beds 

 succeeded each other, and their inclination, ought to be familiar to tlie 

 geological agriculturalist; and, when it was not so, that knowledge ought 

 to be gained, in the first instance, by sections and nrodels. This knowledge 

 was irrdispensable ; fur, without it, they would neither know where to find 

 the material required, nor, when found, be able to get it. Then, again, it 

 was very important to kuow under what circumstances certain rocks, 

 known to be valuable, might be expected to occur in nature. For instance, 

 ther'e were certain igneous rocks, of volcanic origin, which were very 

 valuable bases for soils, and equally valuable for mixing with others. 

 These had, probably, heeir prodirced during a volcanic disturbance, by 

 which they had been forced up iu a melted state to the surface, aud had, 

 perhaps, not only filled up a crevice, but liad also run over iu a sheet like 

 lava. Now, it was quite clear that a person ignorant of its geological 

 relations, wishing to obtain this material, would be puzzled by its depar- 

 ture from the ordinary pheuomena of strata, and he might waste both time 

 and money, without succeeding at last in reaching the valuable rock. 

 Volcanic rocks of this kind might thus lie either vertically or horizontally ; 

 hut it mrrst be obvious, that very ditl'ereut operations would be required in 

 each case to obtain them. A dilliculty in obtaining them, arising from 

 geological ignorance, was the frequent cause of many valuable veins ot 

 igneous r-ock being neglected, or unknown. The mixture of these volcanic 

 rocks, with others that were stratified, almost always improved the soil; 

 but not invariably, as there were some exceptions to the almost universal 

 rule, of their beiug easily decomposable by exposure at the surface. 



There was one important process in agriculture, often made use of, 

 though not always with similar results— viz. : deep ploughing. By this 

 process, the soil at the surface was mixed with that beneath it, and a large 

 proportion of the subsoil brought to the surface. This was sometimes 

 beneficial, and at others mischievous. Unless the origin of the subsoil 

 was known, it was impossible to determine beforehand whether it would 

 be useful, or otherwise. Generally speaking, it was useful ; because the 

 soil was ordinarrly derived from the subsoil ; and if the soil were good, 

 then the subsoil would be good, and it might be mixed with advantage. 

 This, however, was not always the case ; and by deep ploughing, a very 

 dirterent and inferior material might sometimes be turned up. How use- 

 ful, then, must be that knowledge, by which the certain result of such a 

 treatment of the soil might be previously determined. [The learned pro- 

 fessor illustrated this point by a reference to several diagrams, in which 

 the subsoil was represented as derived from various materials.] 



The next part of the subject was the soil as connected with water; and 

 there were two cases, in which agriculturally some geological knowledge 

 on this point was important — the one was, when too much water was 

 present in the soil, and it was necessary to get rid of it ; and the other 

 was in the way of irrigation, wher-e soils received too little water, or did 

 not retain a sufficiency fur the purposes of vegetation. Plants differed 

 enormously as to the quantity of water they required. Soils, which, ia 

 this respect, were admirably adapted for oue kind, were utterly unfit for 

 another species— some plants grew well on soils where others would no^ 

 p-row at all. In these questions, then, a consideration of the nature of thfc 

 crop desired, and the climate in which it had to be growu, was indispens« 

 able. Draining, also, was connected with geology— both surface drainage 

 and deep drainage ; aud the methods of obtaining a supply of water, being 

 dependent on the nature of the earth's crust, were equally connected with 

 that science. Drainage involved one or two other points. Mhen it re- 

 lated to the drainage of large districts, it was a subject of the deepest im- 

 portance, aud then it naturally came more under the head of engineering 

 than agriculture. Both draining on a large scale, and the obtaining of 

 water o'u a large scale, for the supply of our towns aud cities, were sub- 

 jects of the greatest engineering importance ; but he intended now rather 

 to consider the general subject with refereuce to agriculture. In the first 

 place, then, he would touch upon the use of water to plants, which was 

 very simple and easily understood. Plants could not live without it, and 

 they derived it partly from the air and partly iVora the earth. They also 

 obtained with the water other substances, which were important. None 

 of the plants, which were of value to the agriculturalist, would bear a 

 continual exposure to the presence of water. A great deal of mischief 

 resulted from too much water, although injury was also the result of a 

 want of it. This element came exclusively from the clouds in the 

 shape of rain, or snow. The melting of the snow on the mountains, aud 

 tributary rills produced by natural drainage, formed brooks and streams, 

 aud ultimately rivers. Springs caine out upou the surface, without being 

 apparently connected with the fall of rain, but they were derived from it. 

 The rain was absorbed by certain beds, and often emerged at a great dis- 

 tance, in obedience to certain mechanical laws. [The formation of springs 

 was then illustrated by reference to a number of diagrams ; and, by the 

 same means. Professor Ansted showed in what manner irregularities of 

 surface (ihe permeable beds lying in a favourable direction) produced 

 natural drainage.] 



Where there was no natural drainage, the artificial operation connected 

 itself inevitably with the circumstauces under which the superfluity of 

 water occurred. One of two things ordinarily would have to be done; 

 they would either have to get rid of the superficial surface-water, aud that 



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