xxii FIFTH REPORT -1835. 
5. Accurate determinations of the conducting powers of differ¬ 
ent solids, liquids, and gases ; distinguishing from the effects of 
radiation (if any) in or through them; and examining the modi¬ 
fication (if any) which the ratios of the conducting powers un¬ 
dergo from difference of thickness, especially when the thickness 
is extremely small*. 
Desiderata mentioned in Mr. Whew ell*s Report on the Mathe¬ 
matical Theories of Electricity, Magnetism , and Heat. 
1 . A comparison of good recent measures of the statical forces 
in electrical experiments (those of Mr. Harris and any others) 
with the Coulombian theory. 
2. A determination of the degree of exactness attained and 
attainable by means of Mr. Barlow’s correcting-plate. 
3. Measures of the rate of increase of the temperature of the 
earth’s mass in descending (both in given places and on the 
average), to compare with similar observations at a future pe¬ 
riod. 
4. A comparison of the observed law of temperatures, as de¬ 
pending on the latitude, with Fourier’s formulae. 
5. Treatises in which the results of the theories here spoken 
of (Coulomb and Poisson’s theories of electricity and magnet¬ 
ism, and Fourier’s theory of heat,) shall be presented in a man¬ 
ner sufficiently elementary to be accessible to mathematical 
readers of common attainments, as, for instance, the readers of 
Newton. 
OPTICS. 
Resolutions of the Committee. 
1. That a sum not exceeding 80/. be appropriated to the con¬ 
struction of a Telescopic Lens, or Lenses, out of rock salt, under 
the direction of Sir David Brewster. 
2. That a sum not exceeding 15/. be placed at the disposal of 
Professor Powell, for carrying on Experiments on the refractive 
indices of different media on the principle of Fraunhofer, as 
recommended in the reports of the Association. 
3. That 30/. be placed at the disposal of Prof. Wheatstone, 
for procuring a Theodolite and Prism to prosecute his researches 
on the prismatic examination of the Electro-Magnetic spark. 
* See for observations on Radiant Heat Dr. Hudson’s paper in the Fourth 
volume of the Association’s Reports , p. 163. 
