14® Mr. Wollaston's Description 
Ys hanging in gimmals was a new experiment, this error was 
supposed to take its rise from some shake in them. They 
were examined; and were altered in various ways. Fixed Y s 
were then made, of the usual form ; others of a larger ; others 
of a more acute angle. The difficulty was still thought to 
continue. Recourse was then had to Y^ in gimmals again, 
which I was unwilling to give up ; and friction-rollers were 
applied to take off some of the weight. Still this error did 
continue in a small degree : yet was that degree so small, as 
not to be discernible at the polar microscope ; nor, as far as I 
could see, at those belonging to the plumb-line ; and some- 
times scarcely so at the others, to whose greater magnifying 
power it seemed to be owing that it was at all perceptible. 
The cause I then supposed to be, in a disposition in the pi- 
vots to gather up the side of the Ys towards which they 
were turned. Yet was that not the cause : for what little mo- 
tion there was, I found afterwards to be in a contrary di- 
rection. 
This led me into discovering, and at last rectifying the de- 
fect. The original idea of hanging the Y s in gimmals, as was 
said before, was derived from Mr. Smeaton; who kindly 
shewed to Mr. Cary those which he had made to a small 
transit instrument for his own use. His ought scarcely, in 
strictness, to be called Ys ; for he had made a little hollow 
on each side where the pivots would touch, as a sort of bed 
to receive them, and make the angle less pinching. This, 
Mr. Cary had imitated : and, though I did not mean he 
should, he did the same to the second pair he made, after 
trying the other kinds. Since it was done, I let them so re- 
main till I got the instrument home ; for I really found all 
