CHAP. VII. DANGEROUS EXPERIMENTING. 113 



the inflammable gas, otherwise it was liable to go out, 

 in consequence, as he imagined, of the contact of the 

 burnt air (as he then called it), or azotic gas, which 

 lodged round the exterior of the flame. If the lamp 

 was moved backwards and forwards, the azote came in 

 contact with the flame and extinguished it. " It struck 

 me," said he, " that if I put more tubes in, I should dis- 

 charge the poisonous onatter that hung round the flame, 

 by admitting the air to its exterior part." Although 

 he had then no access to scientific works, nor inter- 

 course with scientific men, nor anything that could 

 assist him in his inquiries on the subject, besides his 

 own indefatigable spirit of inquiry, he contrived a rude 

 apparatus, by means of which he proceeded to test the 

 explosive properties of the gas and the velocity of cur- 

 rent (for this was the direction of his inquiries) necessary 

 to enable the explosion to pass through tubes of dif- 

 ferent diameters. In making these experiments in his 

 humble cottage at the West Moor, Nicholas Wood and 

 George's son Eobert usually acted as his assistants, and 

 sometimes the gentlemen of the neighbourhood amongst 

 others William Brandling and Matthew Bell, interested 

 in coal-mining attended as spectators. One who was 

 present on such an occasion remembers that, when an 

 experiment was about to be performed, and all was 

 ready, George called to Mr. Wood, who worked the 

 stop-cocks of the gasometer, " Wise on [turn on] the 

 hydrogen, Nichol ! " 



These experiments were not performed without risk, 

 for 011 one occasion the experimenting party had 

 nearly blown off the roof of the cottage. One of 

 these " blows up " was described by Stephenson him- 

 self before the Committee on Accidents in Coal Mines 

 in 1835: "I made several experiments," said he, "as 

 to the velocity required in tubes of different diame- 

 ters, to prevent explosion from fire-damp. We made 

 the mixtures in all proportions of light carburetted 



VOL. III. I 



