400 Scientific Intelligence. 
slate indicates that a change took Bae. in the era of their forma- 
tion from limestone-making seas to mud- listribution seas. ur- 
ing the transition from one to sha other, iron was washed down 
from not distant land, in the state of bicarbonate ora salt of an 
organic acid, over imite areas of the calcareous deposits. 
hese areas so invaded by the spilt during the transition 
epoch, were within interior seas or basins, or marshes, half shut 
off from the ocean. The aiaraans material wherever receiving 
the iron-bearing waters became changed more or less completely 
to ferriferous limestone or ferriferous dolomite, or received pure 
e be 
the conditions here mentioned may have existed through large 
.parts of the era of limestone-making. The fact that the limestone 
is so largely magnesian is good evidence that the-condition of a 
partly confined sea-basin existed at intervals through the era of 
limestone-making; for the magnesia of concentrated sea waters 
dolomite have been the source of that of the magnesian limestone or 
ol 
ricted (BDL Univ., it xii, 70, July 1884) a paper in 
which he discusses from a theoretical standpoint the probable 
distribution of the temperature within the mass of the ice of a 
ivan e commences with considering the coffe ct of a single 
considerable mass of ice, extending from higher to 
ath fe i 
A second diagram shows the supposed effect of a single summer, 
indicating the portion, facsaite Stat above but extending to the bed 
of the glacier lower down, which might be expected to be affected 
by the summer’s heat and thus be brought i a a melting condition. 
Uniting the two diagrams a third is constructed showing, by the 
rere overlapping of the two portions named, first, a lower part, 
the glacier bed, unaffected immedi iately by either winter 
or su mmer; then a part, B, lower down, reduced to the melting 
paesnot ean by the summer and which will a always remain conse- 
quently at 0°; a corresponding part, C, bigher up than A and like 
B extending partly over ys into which the winter’s cold penetrates 
but which is unaffected by the summer and which may remain 
elow 0°; finally, a fourth layer, D (entirely superticial), affected 
both by summer and winter and whose temperature may vary 
y 
from 0° to considerably Suis 0°. In a word, the glacier may be 
- 
. 
