[ 434 1 
I was obliged to differ from the antient plan, in 
adapting it to the harpoon, and have fubftituted hair- 
ropes inftead of hemp, which the antients ufed. I 
have alfo contrived a new lock, much fimpler than 
any of the crofs-bow kind, recommended by Folard. 
By various experiments I found hairs to be very 
durable elaftic fubftances, that cannot be fenfibly 
affeCed by any degree of heat or cold, which the 
human body can bear. I ftretch’d a fingle hair 
on a fiddle three inches beyond its natural length ; 
let it ftand 24 hours ; then relax’d it, and it foon re- 
traced to [its former length. A fingle hair is nei- 
ther elongated nor contraCed by lying in water ; but 
a number of hairs twilled together are fliorten’d 3 
which is owing to the attra&ion of the furfaces, not 
to the abforption of the fuppofed internal cavities of 
the hairs, the exigence of which is dubious. 
The force of this machine may be increafed to any 
neceffary degree, by multiplying the number of 
fprings or ropes, and increafing the length of the 
lever, which turns the windlace, that draws back the 
crofs cord, or in other words charges it. It has all 
neceffary motions, and is contrived to Hands on a 
pedeffal in the head of a boat. It is fo Ample, that 
any perfon may learn how to ufe it in a fliort time ; 
and when once it is fuccefsfully applied, we fhall be 
no longer obliged to the inffrudtion of the Dutch, 
who reckon it their intereff to obftruC our fuccefs in 
every ufeful branch of trade. 
When the ingenious and benevolent members of this 
learned Society, have confided d the importance of this 
machine, and how far it may promote the public 
intereff, I hope they will recommend the ufe of it 
to 
