72 W. Hopkins on Changes of Climate. 
Neither ferricyanid of potassium nor neutral chromate of potash 
cause death, at least not under several hours. his last fact sug- 
gests the possibility of chemically injecting, even while living, 
these and other species of infusoria, by the mixture of proper re- 
agents causing colored precipitates. The precipitation would 
probably take place not only in the surrounding fluid but also in 
the body of the animalcule, thus demonstrating its structure. 
Art. XIII.—On the Causes which may have produced Changes 
in the Earth’s Superficial Temperature; by W. Hoprxtys, 
Esq., M.A., F.R.S., Pres. G.S., and Pres. Cambridge Phil. Soc.* 
Havine discussed the operation of internal and external causes 
on the temperature of the surface of the earth, I now proceed to 
the consideration of the influences of superficial causes depend- 
ing on the configuration of land and sea, and on the oceanic cul 
rents which result from such configuration, or are greatly modi- 
fied by it. The admirable map of isothermal lines by Humboldt 
and Dove, embodying, as it does, all the best-established observa 
tions on temperature in all the accessible regions of the earth, 
affords us data for this investigation far superior to all we have 
hitherto possessed. Every geologist is aware how long and ably © 
Sir Charles Lyell bas advocated the efficiency of the above-met- — 
tioned causes of change of climatal conditions; but before the — 
publication of this isothermal map, the geologist had no adequate — 
means of estimating numerically the effects which these causes 
were capable of producing. The want of this quantitative eval- | 
uation of the intensity of assigned causes has hitherto necessarily _ 
given to the theoretical views founded upon them much of 4 — 
conjectural character, which it is my object with the improved 
means we possess, as far as possible to remove. | 
very separate configuration of land and sea which we may — 
suppose to have existed at any assigned geological period would | 
strict myself to the examination of those hypothetical case’ 
which, according to the general views of different geologists 
may have been actual cases during the later periods of geological 
history ; and my more especial object will be, moreover, to ascel- | 
tain whether any of these supposed configurations will enable "S — 
to account for the cold of the glacial period in our own region of 
western Europe ; and, if so, which of them must be regarded ® _ 
most effective for this purpose. ai | 
* From the Quarterly Jour. Geol, Soc., viii, p. 56.—In citing this memoir, we omit | 
Part I, which treats of the Siang gg Barth's jotaale Heat and of the Het 
radiating from external bodies on the Earth’s superficial temperature 
gument is mentioned in this Journal, [2], vol. xiv, p. 282.—Eps. 
