Art. VI, Description of a self-acting Blowpipe. By 
Mr. H. B. Leeson. 
Ir has, I believe, before been observed that bottles of Indian Rub- 
ber might be expanded to a considerable size by condensing air 
into them: Tam not, however, aware that bottles so filled with con- 
densed air have been applied to the purposes of a Blowpipe. 
The bottles I make use of vary in weight from half to three- 
quarters of a pound, and may be readily procured at the Stationer’s. 
To prepare them they should be boiled in water till completely 
softened, which, if they are put into water already boiling, will 
generally be accomplished in ten minutes or a quarter of an hour. 
They must then be taken out and suffered to cool, when a brass 
tube may be fitted into the neck of the bottle, having a small 
cock screwed into it at one end, by which it may be connected with 
the condensing syringe, and to which the blowpipe jets may be 
attached. There should be a milled projection on the side of the 
tube, for the purpose of more firmly attaching the bottle to it, 
which may be effected by passing a ligature of waxed string round 
the neck of the bottle on each side of the above-mentioned pro- 
jection. 
The bottle must next be filled with condensed air. After a few 
strokes of the syringe a blister will be observed to form, which will 
gradually enlarge till the greatest part of the bottle (which must be 
selected uniform in substance, and free from defects,) has extended 
to asimilar substance. The condensation should not then be con- 
tinued farther. 
Bottles of the size I have mentioned will generally extend from 
fourteen to seventeen inches in diameter without bursting ; and 
Thave occasionally extended them much beyond these dimen- 
sions ; but in this the operator must, of course, be entirely directed 
by his own observations. 
The Indian rubber varies in its quality. There is one sort which 
appears of a blacker hue before extension, but becomes very thin 
and almost transparent on condensing air into it, whilst there is 
