426 * Proceedings of the Royal Society 
One of the knobs measured in height above the fractured 
surface five-eighths of an inch, and had at its base an area of 
about 3f inches in diameter. The other knob measured in height 
four-tenths of an inch, and had at its base an area of about 
inches. 
Supposing these knobs to be exact cones, there would be 2‘3 cubic 
inches in the former, and '53 cubic inches in the latter, — making- 
altogether 2- 83 cubic inches. But as the tops were rounded, one- 
third should be added to this result, — making altogether 3-77 cubic 
inches. With regard to the amount of matter deposited by the 
three remaining drops, it was scarcely appreciable, so that the 
cubic contents of the whole deposit may be very safely assumed as 
not having exceeded five cubic inches. 
Such having been the amount of growth of the stalagmite 
during forty-four years, it occurred to inquire how long, at the 
same rate of growth, it had taken for the whole stalagmite to be 
formed. In the part of it now at the College, to say nothing of 
the contents of the trunk still in the cave, there are 44 cubic feet, 
or above 76,000 cubic inches. If this amount of calcareous matter 
had been deposited at the same rate as the 5 cubic inches during 
the last forty-four years, the whole stalagmite would have required 
the astounding and incredible period of more than 600,000 years 
for its formation. 
There are several circumstances, however, deserving of notice, 
which show how little such a calculation is to be relied on, — though 
at first sight it is perhaps quite as plausible as many other calcula- 
tions of a similar kind. 
It assumes that during the whole time of the formation of the 
stalagmite, the calcareous matter had been deposited at exactly the 
same rate as during the last half-century ; in other words, that the 
supply of calcareous water to this part of the roof had been always 
exactly the same. There is, however, nothing to prove that this 
was the case; — it is, moreover, not in the least likely to be true. 
Indeed, the great probability is, that the supply of water to any 
one spot in the roof would be much greater at first than afterwards. 
The porous limestone rock of Bermuda becomes hardened and 
encrusted by the rain-water percolating through or over it, and 
the rapidity of this process was marvellous. Lieut. Nelson of 
