The Writings of Benjamin Franklin. 161 



" round a tumbler, with strings of the same, from each side, 

 " meeting above it in a knot at about a foot distance from the 

 " top of the tumbler, Then putting in as much water as 

 " would fill about one-third part of the tumbler, I lifted it up 

 " by the knot, and swung it to and fro in the air ; when the 

 " water appeared to keep its peace in the tumbler as steadily 

 " as if it had been ice. — But pouring gently in upon the water 

 " about as much oil, and then swinging it in the air as 

 " before, the tranquility before possessed by the water, was 

 " transferred to the surface of the oil, and the water under 

 " it was agitated with the same commotions as at sea. 



" I have shewn this experiment to a number of 

 " ingenious persons. Those who are but slightly acquainted 

 " with the principles of hydrostatics, &c, are apt to fancy 

 " immediately that they understand it, and readily attempt 

 " to explain it ; but their explanations have been different 

 " and to me not very intelligible. — Others more deeply 

 " skill'd in those principles, seem to wonder at it, and promise 

 " to consider it. And I think it is worth considering : For 

 " a new appearance, if it cannot be explain'd by old 

 " principles, may afford us new ones, of use perhaps in 

 " explaining some other obscure parts of natural knowledge. 



" I am, &c„ B. F." 



I do not know whether it is generally known that water- 

 tight compartments of ships are an ancient invention, as the 

 following passage will shew : — 



" Works," vol. II., p. 171. 



"While on this topic of sinking, one cannot help 

 " recollecting the well-known practice of the Chinese, to 

 " divide the hold of a great ship into a number of separate 

 " chambers by partitions tight caulked (of which you gave 

 " a model in your boat upon the Seine) so that if a leak 

 " should spring in one of them, the others are not affected 

 " by it ; and though that chamber should fill to a level with 

 " the sea, it would not be sufficient to sink the vessel . 



<k But our sea-faring people are brave, despite danger, and 



