364 Miscellaneous Intelligence. 
6. Preparation of Caoutchouc.—Mr. T. Hancock, has succeeded, 
by some process, the results of long investigation, but which he 
has not published, in working caoutchouc with great facility and 
readiness. It is cast, as we understand, into large ingots, or cakes, 
and being cut with a wet knife into leaves or sheets about 3 or +4; of 
an inch in thickness can then be applied to almost any purpose for 
which the properties of the material render it fit. The caoutchouc 
thus prepared is more flexible and adhesive than that which is gene- 
rally found in the shops, and is worked with singular facility. Re- 
cent sections made with a sharp knife or scissors, when brought to- 
gether and pressed, adhere so firmly as to resist rupture as strongly 
as any other part, so that iftwo sheets be laid together and cut round, 
the mere act of cutting joins the edges, and a little pressure on them 
makes a perfect bag of one piece of substance. ‘The adhesion of the 
substance in those parts where it is not required is entirely prevented 
by rubbing them with a little flour or other substance in fine powder. 
In this way flexible tube catheters, §c., are prepared ; the tubes being 
intended for experiments on gases, and where occasion might require 
they should sustain considerable internal pressure, are made double, 
and have a piece of twine twisted spirally round between the two. 
This therefore is imbedded in the caoutchouc, and at the same time 
that it allows of any extension in length of the tube, prevents its ex- 
panding laterally. 
The caoutchouc, is in this state, exceedingly elastic. Bags made of 
it as before described, have been expanded by having air forced into 
them until the caoutchouc was quite transparent, and when expanded 
by hydrogen they were so light as to form balloons with considerable 
ascending power, but the hydrogen gradually escaped, perhaps 
through the pores of this thin film of caoutchouc. On expanding 
the bags in this way the junctions yielded like the other parts, and 
ultimately almost disappeared. 
When cut thin, or when extended, this substance forms excellent 
washers, or collars for stop-cocks, very little pressure being sufficient 
to render them perfectly tight. Leather has also been coated on one 
surface with the caoutchouc, and without being at all adhesive, or 
having any particular odour, is perfectly water tight. 
Before caoutchouc was thus worked it was often observed how 
many uses it might in such a case be applied to; now that it is so 
worked it is surprising how few the cases are in which persons are 
induced to use it. Even for bougies and catheters it does not come 
into use, although one would suppose that the material was eminently 
fitted for the construction of these instruments. 
7. Magnetic Intensity of a Chronometer——A remarkable example 
of the magnetic intensity of a chronometer has just appeared in 
Vol. X., PartI., of the Transactions of the Royal Society of Edin- 
burgh. Mr, Harvey, the author of the investigation, by employing 
