34 
REVIEW. 
this dried soil, and add to it, by means of a quill, a drop or two of pure water, 
if distilled water can be had, so much the better. Weigh the whole a second 
time, which will now be a few grains above ten. Take out the weight of the 
water from the scale, leaving in the weights of the dried soil, and suspend the 
beam, so that the scale c, may rest on the lid of the tin vessel, in which the water 
is still kept boiliug : then with a stop watch note the exact time, which the added 
water takes to evaporate, as will be shown by the beam of the balance becoming 
level. Mr. Johnson found that soils requiring less than 25, or more than 50 
minutes, to evaporate the added water, and bring the balance to a level, wefe 
always proportionably unproductive; the first from having too much flinty sand, 
and consequently no texture fitted for retaining water; and the second from 
2 
having too much clay, and consequently too few interstices to allow the water to 
escape. Rich soil, treated in this way, required thirty-two minutes to bring the 
beam to a level; chalk twenty-nine minutes: poor flinty soil twenty-three 
minutes, and gypsum only eighteen minutes. 
A very fertile soil from Ormiston, Haddingtonshire, containing in 1000 parts, 
more than half of finely divided materials, among which were eleven parts of 
limestone soil, and nine parts of vegetable principles, when dried in a similar 
way, gained 18 grains in an hour, by exposure to moist air, at the heat of 62 
degrees Fahr. while 1000 parts of a barren soil, from Bagshot Heath, gained 
only three grains in the same time. 
Mr. Johnson farther found, that 100 parts of burnt clay, when exposed in a 
dry state for three hours to air saturated with moisture, at 68 degrees, took up 
29 parts of water, that gypsum, in similar circumstances, took up only 9 parts, 
and chalk only 4 parts.” 
“ Another method of testing the texture of soils is, by taking what is termed 
their specific gravity : that is, comparing what they weigh in air, with what they 
weigh in water. Sufficient accuracy for practical purposes may be obtained by 
drying two different soils at an equal distance from a fire, or in an oven, at the 
same time, and then weighing in the air a pound of each, in a thin bladder with 
a few holes near its top or neck. When the weight has thus been obtained in 
the air, the bladder may be put into w r ater, letting it sink low enough to permit 
the water to enter through the holes into the neck, in order to mix with the dried 
specimen of the soil. The weight in water divided by the difference of the two 
/ 
