angles (fig. 44), either-avith- 
—s € 
spective position, of which 
- the near vertical edge, 
x 
J. LeConte.on the Descent of Glaciers. 335 - 
On combining the twérect- ia ht 
out a stereoscope or by using 
the upper or lower stage of 
the sliding instrument, I find *. 
that the resulting figure al- 
ways presents itself im @ per- 
s 
might be expected, appears shorter than the remote one. When 
the most perfect and steady effect is obtained the upper and lower © 
edges appear as straight lines and the whole perspective figure 
seeming to be a plane. But sometimes in beginning the observa- 
tion and occasionally when the eyes have grown fatigued, these 
lines assume the concave direction mentioned above, and the re- 
sultant figure has the aspect of a bent or warped surface. Imay 
add that the perspective effect is clearly seen when the same 
figures are combined by means of one of Wheatstone’s or Brew- 
ster’s stereoscopes. 
Notr.—In the preceding No. on page 216, the right-hand figure of 
the twin diagram 25, should have been reversed as in 26. 
(Zo be continued.) 
Art. XXIX.—Remarks on the Rev. Henry Moseley’s Paper, 
“On the Descent of Glaciers ;’ by Joun LeConre, M.D., 
Professor of Nat. Philos. and Chem. in the Univ. of Georgia. 
Tue Abstract of the Proceedings of the Royal Society for 
April the 19th 1855, published in the “ Philosophical Magazine ” 
for July, 1855, (4th Series, vol. x, p. 60 et seq.,) contains a very 
ingenious communication from the Rev. Henry Moseley. In this 
paper it is shown, by the application of established mechanical 
principles, that a solid body resting upon an inclined plane, whose 
ngle of inclination is /ess than the limiting angle of resistance, 
upwards. The effect of its extension will, therefore, be to cause 
the lower of the two bodies to descend whilst the higher remains 
at rest. ‘The converse of this will result from contraction: for 
