3 699 
“The means of the intermediate months are almost exactly that 
of the whole year, and the temperature during the three winter as 
well as the three summer months most remarkably uniform. 
“This is precisely that distribution of temperature over time 
which ought under such circumstances to give rise to well-defined 
and intense waves of heat and cold; and I have little doubt there- 
fore that this is the true explanation of your phenomenon. 
** T should observe, that in the recorded observations of the Ca- 
therinenbourg observatory, the temperatures are observed two-hourly, 
from eight a.m. to ten p.m., and not at night. The mean monthly 
temperatures are thence concluded by a formula which I am not 
very well satisfied with; but the error, if any, so introduced must 
be far too trifling to affect this argument. The works whence the 
above data are obtained are, ‘ Observations Météorologiques et 
Magnétiques faites dans Vintérieur de ?Empire de Russie,’ and 
‘ Annuaire Magnétique et Meétéorologique du Corps des Ingénieurs 
des Mines de Russie,’ works which we owe to the munificence of 
the Russian government, and which it is satisfactory to find thus 
early affording proofs of utility to science in explaining what cer- 
tainly might be regarded as a somewhat puzzling phenomenon, 
as it is one highly worthy of being further studied and: being 
made the subject of exact thermometric researches on the spot, and 
wherever else anything similar occurs.” 
Sir John Herschel then states, that since he began this letter he 
had examined some old documents and found the paper which ac- 
companied his letter. ‘‘The date of this manuscript,” he adds, ‘‘ as 
nearly as I can collect it from collateral circumstances, must have 
been somewhere about the year 1829, or rather before than after. 
“ T remain, &c., 
“J. F. W. Herscuer. 
“* P.S. Thermometric observations in the Steppes, of the mean 
monthly temperature of the soil at different depths from one to 100 
feet (at Forbes’s intervals), would be most interesting. At Cathe- 
rinenbourg the mean temperature of the air being 33°°6 Fahr., no 
permanently frozen soil would probably be reached, but a very little 
more to the northward that pheenomenon must occur. 
“ The ‘ thinning out’ of the frozen stratum would be most inter- 
esting to trace, but in thinning out by decrease of latitude it might 
possibly at the same time ‘ dip’ beyond reach, all above it being oc- 
cupied by soil subject to the law of periodic frost and thaw, and 
giving room under favourable circumstances to ice-caverns, pits, or 
galleries. What determines the distinct definition of the hot and 
cold alternating layers is the exceedingly peculiar form of the curve 
of the monthly temperatures as given in the tables above referred to.” 
3. “On some Phenomena observed on Glaciers, and on the in- 
ternal temperature of large Masses of Ice or Snow, with some Re- 
marks on the natural Ice-caves which occur below the limit of per- 
petual Snow.” By Sir John Herschel, Bart., F.G.S., &c. 
