REPORT ON ELECTRICITY^ MAGNETISM, AND HEAT. 
33 
our telescopes can penetrate; but how little can we learn about 
the effects of heat or chemistry, of electricity and magnetism, 
in any substances except those which we can handle ! In the 
case of heat, we can hardly catch any indications of its amount 
either above or below a thin crust at the earth’s surface to which 
we are confined. 
Yet in these cases theory is especially to be cultivated, be¬ 
cause its calculations are the only instruments by which we can 
reach into other parts of our system;—by which we can pass the 
bounds of space and time which at first sight appear allotted us. 
Something has been done in this way: the magnetic changes 
which the globe of the earth undergoes have long been studied, 
and will now be studied still more ; the characters in which the 
electricity of the upper regions of the atmosphere is written, 
may, perhaps, soon be more clearly interpreted than they yet 
have been ; and, with regard to heat, Fourier has shown, that if 
we had ancient observations of the rate of increase of tempera¬ 
ture in descending, to compare with those recently made, we 
should be able to infer the actual temperature of points at a di¬ 
stance below the surface, and the former temperature of the 
surface. 
All these prospects afford reasons both for further cultivating 
the theories of these subjects and for making accurately those 
observations which the theories point out as important elements 
of calculation. In the course of this Report some tasks of both 
kinds have been indicated as more peculiarly desirable ; and I 
will conclude by again stating them as briefly as possible. They 
are such as follow: A comparison of good recent measures in 
electrical experiments (those of Mr. Snow Harris and any 
others) with the Coulombian theory; a determination of the 
degree of exactness of compensation attained and attainable by 
means of Mr. Barlow’s correcting plate; the measure of the 
rate of increase of temperature of the earth’s mass in descend¬ 
ing (both in given places and on the average), to compare with 
similar observations at a future period; the comparison of the 
observed law of temperatures, as depending on the latitude, with 
Fourier’s formulae; and, finally, as a humble but most useful 
step, the production of treatises in wdiich the results of the 
theories above spoken of, (Coulomb’s theories of electricity and 
magnetism, and Fourier’s theory of heat,) shall be presented in 
a manner sufficiently elementary to be accessible to mathema - 
ticians of common attainments, as, for instance, to the readers 
of Newton. 
Note .—The statement made in p. 31, that an increase of 
temperature in descending can result from nothing but a central 
1835. " d 
