Beck^ Oil Universal Screw. 
95 
these are three small pieces of steel (a), so mounted as that_, 
after the necessary thread has been cut upon them^ they can 
be taken out^ hardened and tempered^ and when replaced 
maybe adjusted exactly by the small screw {b) to Whitworth's 
gauges. 
I found it impossible to make either of the cutting gauges 
out of solid metal, because the process of hardening and tem- 
pering made so variable an alteration as not to be compensated 
in any way. 
Any maker, then, who wishes to adopt the "universal 
screw," should — 
First. Obtain the two ring and plug standard gauges and 
the hob made by Whitworth. 
Secondly. His screw-tools should be cut up in a screw- 
cutting lathe, or by somewhat similar mechanical means; 
and 
Thirdly. He must finish his work with adjustable screw- 
cutting gauges, to correct any error arising from the wear of 
the screw -tool. 
As I have stated before, it is of some consequence to 
microscopists that the standard size for the universal screw, 
which has been already recommended and published, should 
be now rigidly adhered to ; and I may say my chief reason 
for making the foregoing remarks is, because I hold an opi- 
nion that, at the last meeting of this Society, a proposition 
was rather hurriedly carried, recommending the use of a steel 
tap, which differs from Whitworth's standard gauges, is in- 
capable of working properly, and the sole advantage of which, 
so far as I can see, is its saving the maker one or two pounds, 
an amount that would be entirely swamped in a few months' 
work. 
[As the above paper referred to a subject in which the 
Society had taken an active part, it was referred to the com- 
mittee who had reported on the subject of a universal screw 
for microscopes, and the following remarks by the reporter 
to that committee, Mr. Brooke, have been appended.] 
As some remarks contained in this paper imply a want of 
due consideration on the part of the committee to whom the 
subject of the standard screw was referred, in substituting a 
tap and pair of screw-tools for the cylindrical gauges and 
hob recommended in their first report, it appears not unde- 
sirable to state the motives which induced them to adopt this 
course. 
It is unquestionable that an exact counterpart of the hob 
TOL. VII. i 
