208 PHILOSOPHICAL TRANSACTIONS. [aNNO I746. 



minous effluvia very plentifully, and rather iir a greater degree than the glass 

 tube. 



If we conclude with the English philosophers, that fire is mechanically produ- 

 cible from other bodies, by collision, attrition, &c. or, according to Sir Isaac 

 Newton, by putting the sulphureous particles of bodies into a very strong vibra- 

 tory motion ; by which means they become hot and lucid, i. e. affect us with 

 ideas of light and heat ; on this supposition may we not conclude, that the action 

 on the glass tube, when it is rubbed, by putting the parts of it into such a vi- 

 bration, and consequently agitating violently the sulphureous particles in it, may 

 heat and kindle them ? and may it not also be supposed, that when the air is in 

 a due state, nitrous or other particles in the air may contribute to the kindling 

 them ? or perhaps, rather that subtil, active, elastic substance, which Sir Isaac 

 Newton supposes to be the cause of the refraction, &c. of light, and which 

 communicates heat to bodies, and is universally difl^used; these effluvia being 

 thus agitated and conveyed by a non-electric body intervening, in a due quantity, 

 to the vapour of the warmed spirit, may be supposed to kindle them, without 

 exciting any originally resident fire in the body immediately communicating with 

 them, the luminous effluvia from the finger, or ice, &c. when brought near 

 the inflammable body, being, as far as we can perceive, of the very same kind 

 with those which proceed from the tube; or there is nothing appearing in them 

 which may lead us to suspect they are not the very same, though in a greater 

 quantity than what can come from the part of the tube approached with the end 

 of our finger. 



If we conclude, with some of the foreign philosophers, Boerhaave, Homberg, 

 Lemery, Gravesande, &c. that fire is equally diffused throughout the vmiverse 

 by the Creator, pervading the interstices of all bodies, and that there is no fire 

 mechanically produced de novo; then, may we not conclude, that whereas, by 

 attrition of the glass tube, there is produced a very quick and strong vibration 

 of its parts, which must necessarily affect the fire contained in its vacuities, by 

 compression and relaxation; so that, as Boerhaave expresses it, there must be, 

 in the bodies thus agitated, and in the fire contained in its pores, an ejcceedingly 

 great motion excited, and the surrounding fire, from both these causes, must be 

 agitated, and so much the more violently the nearer it is; may we not con- 

 clude, that its force will be hereby sufficiently increased to kindle the spirit to 

 which it is conveyed? 



In this, as in the former hypothesis, Dr. M. would not exclude the elastic 

 materia subtilis from being supposed to have an influence on the effluvia. Which 

 ever of the two hypotheses we embrace, Dr. M. inclines to think, that the kin- 

 dling fire rather proceeds from the excited tube. 



Tooting, Feb. 15, 1745-6. 



