348 
POPULAR SCIENCE REVIEW. 
How to Drill Glass. — An ingenious method of drilling glass, which was first 
described in Hardwicke’s Science Gossip and quoted by the Chemical Neivs , 
has elicited from Dr. Lunge an account of another means which he has 
found extremely simple and efficient. It is simply the employment of dilute 
sulphuric acid — and he found it, on trial, to answer much better than the 
method referred to. Not only, it appears, is the efficacy of the cutting tool more 
increased by sulphuric acid than by oil of turpentine, but also, strange as it 
seems, the tools (files, drills, &c.) are far less rapidly destroyed by being used 
with the acid than with the oil. He also found it stated that, in the 
engineering establishment of Mr. Pintus, at Berlin, glass castings for pump 
barrels, &c., were drilled, planed, and bored, just like iron ones, and in the 
same lathes and machines, by the aid of sulphuric acid. As to drilling, Dr. 
Lunge can fully testify to the efficacy of that method. Whenever he wants, 
say, a hole in the side of a bottle, he sends it, along with some dilute (1 : 5) 
sulphuric acid, to the blacksmith, who drills in it, with a hand-brace, a hole 
of ^-inch diameter. This hole is then widened to the required size by means 
of a triangular or round file, again wetted with the acid. He also finds a 
great help in the latter when making graduations on litre flasks, &c. There 
is hardly any smell perceptible during the work, which proves how little the 
acid acts upon the tools, undoubtedly owing to their being tempered ; but 
each time after use, he takes the precaution to wash and dry the files at once, 
and he has so far observed no sensible deterioration in them. 
~ Transparency of Metals at a bright Red Heat. — Dr. Adriani has written a 
letter to a contemporary relative to the reported discovery of Father Secchi, 
that metals at a red heat are transparent. He states that the fact that iron, 
steel, and also platinum and copper, are transparent while at a bright red 
heat, has been known long since not only to practical engineers, but, as re- 
gards iron, steel, copper, and platinum, to workers in these metals. The 
account given of the manner in which M. Secchi found out this property of 
iron is as follows : — The reverend Father hadjordered a strong iron tube to 
be made. As it was intended for an apparatus requiring a vacuum, it was 
essential that this tube should be perfectly airtight : and as Father Secchi 
had some doubts about its soundness in this respect, in order to set these at 
rest, the tube was made red-hot and taken into a dark place, when he 
clearly perceived through the iron, which was half a centimetre thick, 
a crack inside the tube, and which did not reach to the outer surface. 
It is rather curious that the fact of the metals above alluded to (to which 
Dr. Adriani says he has reason to believe that gold may be added) becoming- 
transparent at red heat should have escaped the notice of scientific men. 
It requires, however, a good bright red heat ; but the transparency of the 
metals is, he says, evident thus even in daylight, as he knows from his own 
experience, while working many years ago in an engineering establishment 
attached to a large sugar refinery. 
The Bisulphide of Carbon in Coal-gas. — The valuable researches which 
have just been published by Professor Alfred Gr. Anderson, demonstrate 
beyond all question the imperfection of the apparatus at present employed 
in the estimation of bisulphide of carbon in coal-gas. We cannot here 
enter into details of this chemist’s enquiries, but we may state that they 
support two conclusions, which are thus stated by the author .- — 1. That in 
