A. M. Mayer—Boundary of a Wave of Conducted Heat. 39 
Exp. Major Axis. Minor Axis. Ratios. 
25 
] 12° 9 1°35 
2 14°0 10°5 1°33 
3 17°75 13°5 1°31 
4 18°25« 14°0 1°30 
5 12°75 9°5 1°34 
6 12°8 9°5 1°34 
7 12°8 9°5 1°34 
8 16°4 11°8 1°38 
1°33 Mean Ratio. 
An opinion on the relative values of the two modes of ex- 
perimenting can only be formed from a discussion of the two 
Series of observations by the method of least squares. It is 
true that the series are not as extended as one would wish for 
the application of this rocess, yet its results are equally fair 
for both. We thus have found that the— 
Probable error of a single determi 
“ faa 
fratios in S.’sseries is 0267 
cc “ce M.’s 3 ‘0170 
ns in the mean ratio “e S's = 0004 
& * Oo4, Mie ah. 3000 
From these figures we infer that Sénarmont’s ratio is barely 
true to a hundredth, while my result can be relied on to that 
figure, and if my measures had been made with a micrometer 
microscope, on a plate protected from unequal radiation, and 
shielded from currents of air, I would have obtained a ratio 
reliable to the third decimal place. : 
© the higher ratio of my determination I attach no impor- 
tance; I attribute it to the peculiarity of this particular crystal, 
for several measures on this plate, with a waxed surface, ‘gave 
pone 
