SUPPLEMENTARY REPORT ON METEOROLOGY. 67 
of summer and the winter’s cold are gradually propagated 
both upwards and downwards; and, in either case, with a 
diminishing intensity according to known laws. The annual 
curve of temperature in the ground is rapidly retarded and 
flattened, until, at a moderate depth, (60 to 100 feet, depending 
upon the conducting power and specific heat of the soil,) it 
sensibly coincides with a straight line, or the influence of 
seasons disappears ; and the same takes place in the atmosphere 
at a great and unknown elevation. 
84. The general principles of the communication of heat have 
led to the conclusions, 1. that the annual range should diminish 
geometrically as the depths below the surface increase arith- 
metically ; 2. that the retardation of epochs increases uniformly 
with the depth*. 
85. Both these conclusions of theory have been very satisfac- 
torily verified by the experiments mentioned in the former re- 
port t, and extended since. And what is still more important, the 
verification of these two simple laws includes the introduction 
of certain constants, which may thus be determined a posteriori, 
and the general solution of problems of terrestrial conduction 
obtained. 
86. Instead of merely citing the formule in which the ex- 
pressions of the constants of our globe and system are involved, 
and which are found to express approximately the thermo- 
metric conditions of the strata of our globe near enough to the 
surface to be directly influenced by climateric changes, we will 
endeavour to trace, very generally, the Aind of process by 
which mathematicians have attempted to reduce to law these 
most complicated and involved series of causes. In doing so 
we have a twofold object, which seems peculiarly congenial to 
the nature of such reports as the present; first, to extricate 
from a chaos of symbols (which would deter most persons 
from even tracing the connection of the data assumed, with the 
results announced), such results as apply immediately to the 
physical investigation ; and secondly, to consider how far the 
really fundamental conditions of the problem have, or have not, 
been sacrificed to render the mathematical investigation practi- 
cable at all. 
* See the original works on Heat of Fourier (particularly Mém. de l'Institut, 
1821-22, p. 168) and Poisson, the elementary work of Prof. Kelland, and the 
Report by Prof. Whewell, on the Mathematical Theory of Heat. British 
Association, Fifth Report. 
+ P. 221. The experiments on buried thermometers, near Edinburgh, 
were made in the grounds of Mr. Ferguson, of Raith, by his permission, but 
were suggested and directed by the late Sir John Leslie. See Whewell’s Re- 
port, p. 30; see also article Cuimarr, Encyclopedia Britannica. 
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