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XL. Obfervations upon the EffeSis of Light- 
ning, with an Accoimt of the Apparatus pro - 
pofed to prevent its Mif chiefs to Buildings , 
more particularly to Powder Magazines ; be- 
ing Anfwers to certain Queflions propofed by 
M. Calandrini, of Geneva, to William Wat- 
fon, M. D . F. R. S. 
To the Right Honourable the Earl of Morton, 
P ref dent of the Royal Society . 
My Lord, 
Read June 23, t Very lately received a letter from the 
17 4 ‘ learned and ingenious Monfieur Ca- 
landrini, of Geneva, who has a confiderable employ- 
ment in the Ordnance in that city. In this letter 
Monfieur Calandrini tells me, that he had perufed 
with attention a letter which I wrote to the late Lord 
Anfon, which contained fome fuggeftions tending, as 
I hoped, to prevent the mifchiefs occafioned by light- 
ning to fhips at fea ; and which likewife might, on the 
fame account, be ufeful to powder magazines. This 
letter was printed in the Philofophical Tranfadions *. 
He fays, that he has confidered with fatisfadion the 
real advantages, which may arife from thence to for- 
tified towns, where the quantity of gun-powder may, 
from any accident, endanger the whole fabric of a city. 
This gentleman therefore is defirous of prefenting 
a memorial to the Board of ordnance at Geneva ; in 
which he would be very glad to explain to their fa- 
tisfadion the method I propofe. He has therefore 
* Phil. Tranf. Vol. LII. page 629. 
Vol. L 1 V. D d fent 
