28 OP THE PHTS>'AL PROPERTIES OF THE SOIL. [AppeudlV, 



multiplied by 150, will give very r>early the weight of a cubic foot of the soil in 

 that state. 



4"^. Dstcrminatian of the relative proportions of gravel, sand, and day. — Five 

 hundred grains of the dry soil may be boiled in a flask half full of water till the 

 particles are thoroughly separated from each other. Being allowed to stand 

 for a couple of minutes, the water with the fine matter floatinj^ in it may be 

 poured off into another vessel. This may be repeated several times till it ap- 

 pears that nothing but sand or gravel remains. This sand and gravel is then 

 to be washed completely out of the flask, dried, and weighed. Suppose the 

 weight to be 300 grains, then GO per cent.* of the soil is sand and gravel. The 

 sand and gravel are now to be sifted through a gauze sieve more or less fine, 

 when the gravel and coarse sand are separated, and may be weighed and their 

 proportions estimated. 



These separate portions of gravel and sand should now be moistened with 

 water and examined carefully with the aid of a microscope, with the view of 

 ascertaining if they are wholly silicious, or if they contain also fragments of 

 different kinds of rock — sand-stones, slates, granites, traps, lime-stones, or iron- 

 stones. A few drops of strong muriatic acid (spirit of salt) should also be 

 added — when the presence of lime-stone is shown more distinctly by an effer- 

 vescence, which can be readily perceived by the aid of the glass, — of per-oxide 

 of iron by the brown colour which the acid speedily assumes, — and of black 

 oxide of manganese by a distinct smell of chlorine which is easily recognised. 

 In the subsequent description of the soil, these points should be carefully noted. 



Suppose the sand and gravel to contain half its weight of fine sand, then 

 our soil would consist of coarse sand and small stones 30 per cent., fine sand 

 30 per cmt., clay and other lighter matters 40 per cent. 



5^. Absorbing power of the soil. — A thousand grains of the perfectly, (^r?/ soil, 

 crushed to powder, should be spread over a sheet of paper and exposed to the 

 air for twelve or twenty-four hours, and then weighed. The increase of weight 

 shows its power of absorbing moisture from the air. If it amount to 15 or 20 

 grains, it is so far an indication of great agricultural capabilities. 



6^. Its power of hot ling writrr. — This same portion of soil may now be put 

 into a funnel upon a doubled filter and cold water pourod upon it, drop by drop, 

 till the whole is wet and the water begins to trickle down the neck of the filter. 

 It may now be covered with a piece of glass and allowed to stand for a few 

 hours, occasionally adding a few drops of water, until there remains no doubt 

 of the whole soil being perfectly soaked. The two filters and the soil are then 

 to be removed from the funnel, the filters opened and spread for a few minutes 

 upon a linen cloth to remove the drops of water which adhere to the paper. 

 The wet soil and inner filter being now put into one scale, and the outer filter 

 in the other, and the whole carefully balanced, the true weight of the wet soil 

 is obtained. Suppose the original thousand grains now to weigh 1400, then 

 the soil is capable of holding 40 per cent, of water. J 



7°. Rnpidiiy with which the soil dries. — The wet soil with its filter may now 

 be spread out upon a plate and exposed to the air, in what may be considered 

 ordinary circumstances of temperature and moisture, for 4, 12, or 24 hours, and 

 the loss of weight then ascertained. This will indicate the comparative ra- 

 ]iidity with which such a soil would dry, and the consequent urgent demand 

 for draining, or the contrary. As great a proportion of the water is said to 

 evaporate from a given weight of sand saturated with Avater, in 4 hours, as 

 from an equal weight of pure clay in 11, and of peat in 17 hours — when placed 

 in the same circumstances. 



8°. Power of absorbing h.cat from the sun. — In the '/receding experiment a por- 

 tion of pure quartz sand or of pipe clay may be employed for the purpose of 



• As 500 : 300 :: 100 to 60 per cent. 

 t That is, one filter within another. 

 X 1000 : 400, the increase of weight as 100 : 40*  



