On the Physical Properties of Soil 



187 



p q is B, scale-beam 20 inches in length, p being a ball of 

 lead, by means of which the scale-pan w on the longer arm is kept 

 evenly balanced, so long as weights are not put into it ; this arm 

 of the balance has its movement within a fork-like section made 

 through the upright piece h, of which the fig, hh is the front view : 

 n is of steel, blunt, spade-shaped in its termination, the 36th 

 part of an inch in thickness, and one-third of an inch in breadth 

 below (as corresponding with the breadth of the rectangular 

 piece of moulded earth, to be submitted to trial) ; this little spade 

 is secured to the beam at x, by a pivot^ in such a manner that it 

 always hangs freely straight down. The earth to be examined is 

 now brought under the little spade, weights are put into the scale- 

 pan until the earth is cut through ; in the case of earths whose 

 consistency is small, we must commence with dram weights only ; 

 with earths of great firmness, the weight required will amount 

 to several pounds ; if we give to the beam, from o to 5-, a 

 length of 12 inches, while the pivot-point of the little spade 

 a? is at the distance of one inch from 0, the weight of a single 

 pound put into the scale-pan will exert on the earth a pressure 

 equal to the weight of 12 pounds ; if we repeat the experiment 

 several times, which we can easily do, with the rectangular 

 moulded pieces of the same earth, and take the average of the 

 whole, we shall obtain a result much nearer to the truth. The 

 purest, densest, and heaviest clays to work, which I had oc- 

 casion to examine by means of this instrument, required, in order 

 to crush them, 4j pounds in the scale — consequently, an actual 

 pressure equal to 54 pounds. 



If we designate the consistence found for the compactest clay by 

 the number 100, the consistence of all the other earths may easily 

 be referred to this as the standard ; and thus, independently of the 

 clay itself, we shall be able to institute comparisons between the 

 consistencies of any of the different earths. The principal point 

 is, to form properly and equally worked pieces of the earths to be 

 compared, without too much water ; and this, with a little prac- 

 tice, may easily be accomplished by means of the mould already 

 mentioned. 



The tabular view given at the termination of the following 

 paragraph, contains the consistencies obtained, according to this 

 plan, of the simple soils most frequently employed in husbandry ; 

 a comparative investigation of the firmness of the different kinds 

 of mortar by means of the same instrument, was communicated 

 by me some years ago in an appendix to Alberti's ' Description 

 of the Mountains of VViirtemberg' (Stuttgart, 1826, p. 305), 

 which also appeared in an abstracted form in Schweigger's 

 '^Journal of Chemistry,' in 1827; only, with this difference, 

 that in those experiments, I made n terminate in a steel point, 

 instead of a short spade. 



