( 171 ) 
III. — Observations upon Mr. William A. Bogers' Paper " On a 
Possible Explanation of the Method employed by Nobert in 
Buling Us Test-Platesr * By W. Webb. 
{Taken as read before the Koyal Microscopical Society, 1876.) 
Mr. Kogers says : " The problem is naturally divided into two 
parts: (a) The mechanical operation of moving the plate to be 
ruled over given and equal spaces ; (b) The operation of producing 
on glass, lines of varying degrees of fineness." Mr. Kogers then 
gives an elaborate description of his meritorious efforts to supply 
the exigencies of the first division " (a) and modestly gives the 
results as " the outgrowth of his own experience." 
If Mr. Kogers had availed himself of qualified assistance, the 
fact would have been ascertained that his instrument did not 
supply the primary necessity of elimination of friction, and that his 
" plate against which the precision screw works as a shoulder " is 
not merely unnecessary, and therefore a surplusage, but is posi- 
tively detrimental in creating friction in the initial step of the 
work. Mr. Kogers might also have ascertained that this part of 
his instrument ought to consist only of three pieces — viz., the carrier 
for the glass, the screw to project the carrier, and the bed upon 
which the carrier moves, the bed having one end turned up at 
right angles and tapped for the screw. 
Mr. Kogers may forget, or perhaps never have known, that in 
1861 (before the Koyal Microscopical Society of England had ob- 
tained its charter of incorporation) bands of lines after the manner 
of Nobert, ruled without a screw, were exhibited to the members. 
He is a bold man who ventures to say by what means Nobert 
produces his wonderful and deservedly admired efiects ; not merely 
whether he produces them with or without the use of a screw, but 
whether with or without a diamond; as to which Mr. Kogers 
says, " The evidence seems quite clear that they are ruled with a 
diamond having a knife-edge." 
How Nobert produces his lines is not so much the question as 
the laudable ambition to produce similar lines by some means 
without knowing Nobert's process, and Mr. Kogers is most cer- 
tainly wrong in his assumption of a knife-edge, the cut from 
which, if not immediately covered with balsam and fixed on a slip, 
will sooner or later by the mere vibration of the earth end in dis- 
ruption, and even if balsamed down, the time may come when the 
balsam itself starts from the glass. Nobert's are as good after a 
quarter of a century as when first cut, which is an impossibility 
with knife edge ruling unfilled in ; and to fill in with balsam, 
without first blacking in^ would be, in consequence of the minute 
* Page 74, ante. 
