108 
Mr Troughton’s Nautical Top, 
wide, and on a steel point which descends about half an inch 
below the upper surface of the frustum. 
Mr Troughton, we know, is still continuing his experiments 
upon this subject. His present efforts are chiefly directed to the 
means of preventing the action of the wind, and at the same 
time removing the effect which the recoil of their own wind pro- 
duces ; a thing which, within moderate dimensions, he finds is 
not easily effected. 
The apparatus for putting the top in motion, consists of a 
series of wheels, tlie first and largest of which is put in motion 
by a winch or handle placed in its circumference. The last 
axis which is put in motion, and acquires a great velocity from 
the intermediate wheels and pinions, carries at its lower end a 
hollow square key like the termination of a clock-key. This 
hollow key fits loosely the square axis of the top, so that when 
the one is placed upon the other, and the apparatus put in mo- 
tion by the hand, the top receives the same velocity as the key 
and the axis to which it is attached. As soon as the velocity 
acquired by the top is considered sufficiently great, the whole 
apparatus is quickly raised ; the key leaves the vertical axis, 
and the top revolves alone with an inconceivable velocity. 
In the course of last summer v/e had an opportunity of wit- 
nessing this simple experiment. The top had then the second 
form which we have described ; the images of objects reflected 
from the revolving plate of glass appeared absolutely fixed ; and 
in consequence of the total disappearance of the projecting arms 
which held the outer ring of brass, this ring appeared to be abso- 
lutely suspended in the air, and to surround the top exactly as 
the ring of Saturn encircles the body of the planet. 
The velocity of the circumference of the base has been cal- 
culated at about 30 miles an hour. 
Ei)iXBUs,GHp April 20. 1819. 
