is 8 Mr. Troughton on dividing Instruments. 
When the utmost degree of accuracy is required, I give 
the preference to dividing by lines, because they are made 
with a less forcible effort than dots are ; and also because, if 
any small defect in the contexture of the metal causes the 
cutter to deviate, it will, after passing the defective part, pro- 
ceed again in its proper course, and a partial crookedness in 
the line will be the only consequence ; whereas a dot, under 
similar circumstances, would be altogether displaced. But, on 
the other hand, where accuracy has been out of the question, 
and only neatness required, I have used dots ; and I have done 
so, because I know that when a dot and the wire which is to 
bisect it are in due proportion to each other, (the wire cover- 
ing about two thirds of the dot) the nicest comparison possible 
may be obtained. It may be further observed, that division 
by lines is complete in itself ; whereas that by dots requires 
lines to distinguish their value. 
On the upper side of Fig. i is represented the apparatus 
for cutting the divisions. It consists of three pieces J K L, 
jointed together so as to give to the cutter an easy motion 
for drawing lines directly radiating from the centre, but in- 
flexible with respect to lateral pressure; dd are its handles. 
The cutting point is hidden below the microscope H ; it is of 
a conical form, and were it used as a dotting point, it would 
make a puncture of an elliptical shape, whose longer diameter 
would point towards the centre. This beautiful contrivance, 
now well known, we owe to the ingenuity of the late Mr. 
Hindley of York ; it was borrowed by Mr. Ramsden,* and 
applied with the best effect to his dividing engine. 
* This I learned from that most accurate artist Mr. John Stancliffe, who was 
himself apprentice to Hjn dlev. 
