600 REPORT — 189J. 



thesiB,' wbicli if he is permitted opportunity he will ' pi-oseciite, improve," and 

 publish.' Some years later he returned to the subject of flame in his tract called 

 ' Lampas,' published ia 1677. 'The flame, as I formerly proved, being nothing- 

 but the parts of the oyl rarified and raised by heat into the form of a vapour or 

 smoak, the free air that encompasseth this vapour keepeth it into a cylindrical 

 form, and by its dissolving property preyeth upon those parts of it that are 

 outwards, . . . producing the light which we observe ; but those parts which 

 rise from the wick which are in the middle are not turned to shining flame till 

 they rise towards the top of the cone, where the free air can reach and so dissolve 

 them. With the help of a piece of glass anyone will plainly perceive that all the 

 middle of the cone of flame neither shines nor burns, but only the outward super- 

 ficies thereof that is contiguous to the free and unsatiated air.' 



What is practically the same theory of flame was worked out experimentally 

 by John Mayow, Fellow of All Souls : this was published a few years after the 

 ' Micrographia.' 



But Mayow went further, and distinctly showed the dual nature of the air. 

 One constituent of air, the nitre air, is concerned in respiration and combustion ; 

 the other will neither support flame nor animal life. The ideas, the names, pro- 

 posed by Hooke and Mayow are so exactly similar that it is impossible to 

 imagine that the work was done independently. The two were working at the 

 same time at Oxford, and Mayow, having been an undergraduate at Wadham 

 under Dr. Wilkins, became the pupil of Willis. Yet Mayow nowhere mentions 

 Hooke's name. A writer in the ' Dictionary of National Biography ' ' has shrewdly 

 observed that Hooke has brought no charge of plagiarism against Mayow, anil 

 even proposed him for the Royal Society four years after the publication of the 

 ' Five Tracts.' Knowing what we do of Hooke's jealousy, it seems exceedingly 

 unlikely that Mayow was merely working out Hooke's ideas. It seems to me 

 probable that Hooke and Mayow worked together under Boyle between 1660 and 

 1662 ; that in Boyle's laboratory they saw and assisted in the experiments which 

 led them jointly to their theory ; that Hooke, busy with other work in London, 

 published the hypothesis in 1(:65 without further verification; and that Mayow in 

 Oxford systematically worked through the e.xperiments on which he based his 

 conclusions. 



Let me briefly show what the experiments were on which Mayow relied. 

 Combustible bodies will not burn in the vacuous receiver of Boyle's air-pump ; 

 they will burn in vacuo or under water when mixed with nitre. There is, there- 

 fore, something common to air and to nitre which causes combustion. The fiery 

 particles in air and in nitre both form oil of vitriol by their union with sulphur ; they 

 both form iron vitriol by their union with pyrites. Rust of iron is produced both 

 by the air and by acid of nitre ; the acids of sugar and honey are formed, and wine 

 is soured, in the same way. The nitre-air (spiritus nitro-aereus), the supporter 

 of combustion and the acid producer, is therefore the same chemical substance 

 whether it exist in the gaseous form in air or is condensed in saltpetre. 



Mayow heated a weighed quantity of antimony by means of a burning glass, 

 and found it increased in weight during the calcination ; - the calcined antimony, 

 he adds, has the same properties as the body prepared by heating antimony with 

 nitric acid ; it is impossible to conceive, he says, whence the increase in weight 

 arises except by the fixation of the particles of nitre-air during the heating. 



The nitre-air does not make up the whole of the air, but only its more active 

 and subtle part, for a candle under a glass will cease to burn while there is still 

 plenty of air left. The experiment by which Mayow shows this is so important 

 that i will quote his words : — 



' Let a lighted candle be so placed in water that the burning wick shall rise 

 about six fingers' breadth above the water ; then let a glass vessel of sufficient 

 height be inverted over the candle. Care must be taken that the surface of the 

 water within the glass shall be equal in height to that without, which may be 



' Mr. P. J. Hartog. 



^ This experiment seems to have been first described by Poppius, Basilica 

 Antimonii, 1625. 



