C 352 ] 
LVI. An Account oj an horizontal Top, in- 
vented by Mr. Serfon, by Mr. James 
Short, F. R. S. 
Read Feb. 6, r ~T~^HE horizontal top, the invention of 
J[ Mr. Serfon, who was unfortunately 
loft in his Majefly's fhip the Victory, is pretty well 
known. This ingenious perfon found, that, when 
this top is fet a-going in the proper way, its upper 
fide, which is polifhed, about two minutes after it 
was fet up, moved in fuch a manner, as to give a 
true horizontal plane j and that this plane was not 
at all difturbed by any motion or inclination you 
give the box, in which it is placed, and therefore 
might be proper to be ufed aboard a fliip j by which 
means feamen might be enabled to take the altitude 
of the fun or bars, in order to find their latitude, 
even tho’ they cannot fee the horizon in thick hazy 
weather. 
Some gentlemen of my acquaintance were of opi- 
nion, that the air had fome fhare of the caufe of 
this horizontally. I therefore applied to Mr. Smeato^ 
who has the befl air-pump I ever faw, all of his own 
invention and conftruction. The pump being at 
this time in the houfe of Mr. William Watfon, who 
had defired the ufe of it for fome electrical experi- 
ments, we went thither ; and having fet the top 
a-going, we put a receiver over it, and immediately 
exhausted the air. 
By repeated trials it had been found, that the top, 
when fet a-going in the open air, played or fpun 
during 
