on the Temperature of Soils. 
145 
the simplest and more useful form in which the criticism can be 
conveyed. 
We require to know, — 
1. The temperature of soils at depths accessible and profitable 
to the agriculturist. 
The thermometer is all sufficient for indicating temperatures. 
It would be advisable that the heat of the surface, and that of 
the soil at every 2 inches in depth, descending to 12 inches, and 
thence to 36 inches, by spaces of 6 inches, should be noted. Self- 
registering thermometers would give the maxima and minima 
temperatures, but these instruments conduce to laziness in the 
observer ; they give no information of the periods of the 24 hours 
when the maxima and minima occur, nor register the continually 
varying increments and decrements of heat at different depths, as 
they are affected by sunshine, or cloud, by rain, wind, and other 
atmospheric changes, which should be diligently and faithfully 
recorded. 
2. The temperature of the air, in the shade, near the earth. 
3. The pressure of the air : for which the barometer suffices. 
4. The temperature of the rain. 
5. The quantity of rain ; ascertained by the rain-gauge. 
6. The quantity of water passed by drainage from a measured 
extent of land, in order to compare it with the ascertained fall of 
rain on its surface. 
There are many situations in which this object could be 
accomplished at a trifling expense, and the knowledge of such 
facts would open a new chapter of the book of nature to our 
view. All that has been written as to the quantity of water dis- 
missed from the earth is too speculative and baseless to merit 
more than a passing notice; and no inquiry into these pheno- 
mena has, I believe, been instituted with the end of making them 
subservient to the practice or science of agriculture. 
7. The dew point ; to be determined at frequent periods of the 
day and night. 
The best known hygrometer is Professor Daniell's, but, though 
simple and true, it has the disadvantage of requiring a manual ex- 
periment for every determination. 
8. The quantity of dew deposited. 
Of the amount of this item in the stock of Nature's fertilizing 
laboratory we are wholly ignorant ; and though aware, as we must 
be, of the difficulty of ascertaining the fact required, there is no 
reason to despair of overcoming it if the attention of the many 
gifted men now attached to the science of meteorology could be 
brought to bear on the construction of a sufficient instrument. 
9. The hygrometric condition of soil. 
By this term is meant the amount of moisture which a soil may 
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