106 
Proceedings of the Royal Society 
that plumbers (employed by the Town-Council) were removing the 
old lead and substituting new in its place, and being also encouraged 
by Professor P. Gr. Tait, who with me visited the spot, to believe 
that the markings which had been discovered were electrically of 
unusual interest, I lost no time in applying to Mr J. D. Marwick, 
town-clerk, for those portions of the leaden covering which con- 
tained the marks in question, with the view of presenting them to 
the Royal Society. 
Mr Marwick was as obliging as prompt in responding to such a 
request, arid sent me the required specimens next day, accompanied 
by the enclosed memorandum written by Mr H., assistant to 
Mr Cousin, city- architect. 
lO^A February 1863. 
The accompanying pieces of lead were taken from the north- 
west side of the lead platform on the roof of the lower part of 
Nelson’s Monument. 
“ The distance between the holes was about nine feet six inches. 
“ Both holes were immediately over a block-tin gas-pipe, which 
is here carried under the lead and boarding of the platform, and 
which was found melted the whole length between the two holes, 
and a foot beyond the north-east hole. 
“ These holes in the lead were evidently directly caused by the 
burning gas from the pipes underneath. 
Fig. 1. 
An.E.HOLE B s.w.hole 
The sketch shows section through the platform between the 
two holes A and B. CD shows the gas-pipe under and between 
them. 
“ From this sketch we might naturally expect a hole melted in 
the lead at A, the pipe being here at its highest level immediately 
under the boarding, only one inch from the lead. 
‘‘ The pipe between C and D would very quickly be melted by 
