PORT al St he eg Oe 
D. Kirkwood—Solar and Sidereal Heat. .- Bet 
In conclusion I give the following table of results, a 
the 
as nearly as possible to the absolute value of Ohm 
earth quad. , 
ame ; 
Date. Observer. Value of Ohm. Remarks, 
1849 |Kirchhoff__.-.--- 88 to ‘90 Approximately. 
S051" Weber 2-22.52. = *95 to ‘97 
18 1-088 From Thomson’s un 
62 [Weber -....-... } 1075 From lange s fale ] Siemen’s unit. 
1863 ; § 10000 Mean of a ts. 
—4/B. A. Committee. ) 993 Corrected ris a zero velocity of coil. 
1870 |Kohlrausch 10196 
970 Taking ratio of quicksilver unit to Ohm 
1873 |Lorenz 962. 
980 Taking ratio of quicksilver unit to Ohm 
1876 [Rowland ----..- ‘9912 Prom a preliminary comparison with the 
: B. A. uni 
[To be continued. } 
Art. XLIII —On Croll’s Hypothesis of the Origin of ae and 
Sidereal Heat ; by Professor DANIEL KirRKWwoo 
THE Quarterly Journal of Science for July, 1877, contains 
an able and interesting article by James Croll, LD., F.RS., 
on the age and origin of the sun’s heat. The theory of as 
Croll may be regarded as a compromise between the mathema- 
ticians, represented by Thomson, Tait and Newcomb, ine the 
geologists of the uniformitarian school, represented by ‘Playfair, 
Lyell, Darwin, etc. The principal points of this remarkable 
paper a 
1. That, as had been estimated by Sir William Thomson and 
others, but twenty million years’ heat could be produced by 
the —_ epee of the sun’s mass. 
w determination has — made by H. F. Weber 
great accuracy. The result 
* Since 
of Zuri ults a befe ae 
at ih, i in “eho ths the the diferent an agree with comparison seems to a been 
made simply with a nas4 of resistance coils and snot with standa modern 
oe n’s Mepis seem to be reasonably exact, bu’ m the table published by the 
tish Association » Oomiadeee in 1864, it seems cue vat that time cer- 
en nearer Fess 
tainty as to its value. He obtains 1 S. U. = ‘9550 —_-——, wileh 18 grea 
or than the British Association determinati i. mae we take the dif- 
ferent ratios of the Siemen's to the British path unit, ranging from “14 
— whee to 1°92 per cent below. In any 
Well with my own. The apparatus used does Sand ot seem to have been of the best 
i con e mes 
Pair of coils is used, seeing that in that case the constant, both of magn effect 
tnd of induction, depend on the ej Sc it nat tt 
cient detaile 
