358 Mr, Deuchar on the Ductility of Glass. [Nov. 
Artic.e VIII. 
An Account of several Circumstances connected with the Ductility 
of Glass. By John Deuchar, MRAI. Ed. Cal. Hort. Soc. and 
Wernerian Nat. Hist. Soc.; and Lecturer on Chemistry in 
Edinburgh.* 
(To the Editor of the Annals of Philosophy.) 
DEAR SIR, Edinburgh, Oct. 18, 1822. 
THE great ductility of glass seems, at an early period of the 
history of that compound, to have been noticed by philosophers, 
but they have entirely overlooked several very important accom- 
panying circumstances. They had, in the construction of the 
thermometer and other instruments, found that a hollow ball 
could be drawn out till it formed a very long tube still hollow ; 
but they made no attempts to ascertain the extent to which the 
ductility of a tube might be carvied without the hollow part being 
closed up, nor if it were at all changed in its relative dimensions, 
Thus their knowledge of the ductility of hollow glass appears to 
have been confined to the observation, that a melted tube drawn 
out by the fingers till it formed very brittle threads, still admitted 
of the air being blown through it. 
But, with regard to solid glass, no experiments whatever 
seem at that early period to have been tried to ascertain its duc- 
tility. This attempt was left for modern ingenuity; at first, 
about 40 or 50 years ago, it was performed by means of the 
fingers ; and the late Mr. Knee, of Edinburgh, was the only 
person who did so to any great extent. A mode, however, was 
introduced about 20 years afterwards, by means of which the 
glass was drawn out upon a wheel with greater rapidity than 
common threads. This method of spinning glass, as it is now 
termed, was exhibited in Scotiand by Mr. Gheri in 1808, by 
Mr. Finn in 1811, and by Mr. Davidson in 1812; and J have 
availed myself of their assistance in drawing such of the speci- 
mens of spun glass, noticed in the present experiments, as are 
not of my own manufacture. : 
I was led to examine the subject from the different appearance 
I observed in the threads drawn from a piece of window glass 
with sharp angles, and those drawn from a circular piece of 
crystal equally transparent ; the former having great lustre, and 
the latter presenting a dull surface. 
Although 13 years have now elapsed since I commenced the 
investigation, during eight of which I have been in the practice 
of showing the experiments in my classes, yet no treatise upon 
® Read before the Wernerian Natural History Society, May 18, 1822, 
