Explosioji of Hydrogen and Oxygen. 105 



the encomiums bestowed upon the contrivances of Gurney, the 

 oil cylinder of Prof, dimming, the layers of wire gauze as sug- 

 gested by WoUaston, ^fec, 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- 



r 



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 hkc 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 hfe. 



I have 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- 

 lowing notes of some of the test experiments are taken from my 



-L 



record. 



The tube was constructed of sheet brass, 6 inches in length 

 and fths 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 introduc- 

 tion 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 mhiute, 

 and it was with difficulty that air could be forced through by 

 blowing with the mouth. It is hardly necessary to remark, that 

 a large cooling surface was thus produced, and that flame ap- 

 plied at one extremity would be far more effectually cooled down 



by it, than by the wire gauze when held over a gas flame, or when 



surrounding ignited gaseous matter, as in the safety lamp. 



The tube was 



Hemmin 



receive stop cocks. In my first experiments, the 



tube was prolonged at each end by a leaden tube about four feet 



Vol. XXXVII; No. 1.— July, 1839, bis. 14 



