calculate the rate of stalagmitic formation ; it is a subject that 
has only lately engaged much attention, hut we will make use 
of what we have. 
Mr. John Curry had observed f of an inch which had formed 
on the edge of some deal boards used in connection with 
the working of a lead-mine at Boltsburn, near Durham. 
These boards, he knew, had only been there fifteen years. The 
particulars will be found in Nature , December 18th, 1873. 
Mr. W. Bruce Clarke called attention to one-eighth of an inch of 
stalagmite having formed on a gaspipe in Poole’s Hole, near 
Buxton, six months after the pipe was placed there. It was so 
placed in March, 1861, eighteen years back. Since then the 
stalagmite boss has increased to 1 T 3 ^ inch ; and on the 24th 
of October, 1878, I obtained permission from the proprietor of 
the cavern, Mr. Redfern, to remove the boss, which I place before 
you to-night. 
I have also an iron nail which had been left by the workmen 
in a forsaken lead-mine, called Rackets, on the road from 
Buxton to Castleton. The nail projected from a plank, and 
intercepted the drip from a stalactite. It has a delicate casing 
of stalagmite, a quarter of an inch in thickness. The branch 
of the mine in which this nail was found February, 1877, was 
worked in ] 805 ; consequently the stalagmite must have formed 
in 72 years. 
There were also careful measurements made by Mr. James 
Farrer in Ingleborough cavern in Yorkshire, in 1845, which, 
compared with those afterwards made by Prof. Boyd Dawkins 
on the same spot in 1873, showed an increase at the rate of 
more than a quarter of an inch in the year. 
If the above-named cases were to be made the data for 
calculating the 1^ inch of stalagmite which divides the 
mammalia in question from the pre-Roman period, the 
Boltsburn case would fix the time at 30 years. The first 
observation in Poole’s Cavern would lead us to accept six years 
for the time employed. But the accretion has not been uni- 
form, for since then it has only increased at a rate that would 
require about 22 years to form the 1£ inch under consideration. 
Whilst, in the case of the nail before us, 432 years would be 
employed in producing the same amount of deposit ; but that 
of Ingleborough would only indicate five years. 
Of course I do not say that any of these cases are to decide 
the time required for stalagmitic formation, but they show that 
it is not necessarily so slow a process as we had been led to 
think. Mr. Pengelly very justly asks, “ Why must the rate of 
accretion in Ingleborough Cave be taken as the measure of 
other caves?” And he says that “it is unsafe to use the rate 
