200 
always been at the same elevation above the sea—that, in 
fact, at one time in its existence it may have been submerged. 
If so, then a much larger quantity of water may have per- 
colated through its roof than there does at the present time ; 
and, further, the amount of carbonate of lime held in sus- 
pension in the water may have been very much greater than 
that at the present time, and the condition favourable to the 
evaporation of the water, and so of the deposition of the lime, 
may have been different. In the first place, the amount of 
carbonic acid gas in the air may have been much greater ; 
and, in the second place, the temperature of the earth or the 
water, or both, may have been higher than at the present 
time. If such were the case, there might have been a very 
rapid deposition instead of a very slow one. The specimen 
which I hand round to be examined is a deposition of 
carbonate of lime, which, in its thickest part, is 14 inch. 
Now, according to the estimate of Mr. Pengelly, if laid 
down in a cave, it would have required 5,520 years for its 
deposition. But, as a matter of fact, this particular piece 
was deposited in a few months. It is a deposit taken out 
of a boiler in a metropolitan factory, and was laid down in a 
few months. 
It will be well here to give a few facts as to the rapid 
deposition of stalagmite in our country in modern times 
and under ordinary circumstances. Mr. John Curry, in 
an article in Nature, December 18, 1873, p. 122, referring 
to Mr. Wallace’s review of Sir Charles Lyell’s Antiquity of 
Man, when speaking of the opinions of the reviewer as 
to the great antiquity of man, based on the rate of stalag- 
mitic deposit, says, “‘Some thirty years ago I procured 
a piece of lime deposit from a lead mine at Bottsburn, in 
the county of Durham. It measured about 18 inches in 
length, 10 inches in breadth, and fully 3 inch thick. It was 
compact and crystalline, and showed distinct facets of crystals 
on its surface, over which the water was running. I had 
indisputable evidence that the deposit had taken place in 
fifteen years. The water from which it was produced issued 
from an adit driven in the little limestone, which is about 
9 feet thick. After leaving this adit the water ran down the 
perpendicular side of a rise for some fathoms on to some 
rock of débris which was lying on the bottom of a hopper, 
whence it proceeded from the upper part of the hopper 
mouth, then perpendiculariy down over two narrowish 
deals, which were set on edge and put across the mouth of 
the hopper to retain the worked material. It was from these 
