Explosion of Hydrogen and Oxygen. 105 
the encomiums bestowed upon the contrivances of Gurney, the 
oil cylinder of Prof. Cumming, the layers of wire gauze as sug- 
gested by Wollaston, &c., have now given place to the safety 
tube of Mr. Hemming, which is in fact a modification of the 
faggot of capillary tubes proposed by Wollaston, 
This tube was first publicly exhibited by Mr. Hemming at 
the meeting of the British Association for the advancement of » 
Science, in 1832, and is fully described in the published. report. - 
The description is quoted by the late Dr. Turner in his Ele-- 
ments, with the remark that all previous modifications, of the ap- 
Paratus “are rendered unnecessary by the Safety Tube lately 
proposed by Mr. Hemming.” An authority like this, and one 
Which has become the guide of so many, will undoubtedly lead 
to the employment of this tube, as well as to its construction, by — 
inexperienced persons ; and without previous care to test its safety 
in the severest manner, its use may be attended with the destruc- 
tion, not only of apparatus, but of life. 
Thave been induced to make these remarks in consequence of 
a terrific. explosion which occurred in my laboratory a few days 
since ; and to show how much care was taken to test the safety 
of the instrument before it was exhibited to my class, the fol- 
wing notes of some of the test experiments are taken from my 
record. 
The tube was constructed of sheet brass, 6 inches in length 
and #ths of an inch in diameter, the size recommended by Hem- 
ming. This was closely packed with iron wire (No. 22), each 
Wire extending through the entire length of the tube. The 
close approximation of the wires was increased by the introdue- 
ton of a pointed rod of the same metal and same length; this 
Was driven forcibly through the centre of the bundle of wires. 
Thus the Spaces between the wires were exceedingly minute, 
and it was with difficulty that air could be forced through by 
blowing With the mouth. It is hardly necessary to remark, that 
. large cooling surface was thus produced, and that flame ap- 
Plied at one extremity would be far more effectually cooled down 
byit, than by the wire gauze when held over a gas flame, or when 
“uttounding ignited gaseous matter, as in the safety lamp. 
The tube was terminated at each end by a female screw to 
receive . stop cocks. In my first experiments, the Hemming’s 
Mabe Was prolonged at each end by a leaden tube about four feet 
Vol, XXXvir, No, 1.—July, 1839, bis. ~ 
