28 ESSAYS BIOGRAPHICAL AND CHEMICAL 



' Touching the Spring of the Air/ in which he describes 

 experiments proving that a volume of air under a pressure 

 of two pounds occupies exactly half the volume that it 

 does under a pressure of one pound. This, although not 

 absolutely true, is yet sufficiently exact to be generalised 

 into a law, which is known by Boyle's name. He finds a 

 reason for this ' spring ' in premising that ' the air abounds 

 in elastic particles, which being pressed together by their 

 own weight constantly endeavour to expand and free 

 themselves from that force ; as wool, for example, resists 

 the hand that squeezes it, and contracts its dimensions ; 

 but recovers them when the hand opens, and endeavours 

 at it even while that is shut.' 



In truth Boyle delighted in mechanical explanations. 

 The titles of his papers attest this. We find, 'The 

 Mechanical Production of Magnetism ' ; ' The Mechanical 

 Production of Electricity'; 'The Mechanical Causes of 

 Precipitation'; 'The Mechanical Origin of Corrosiveness 

 and Corrosibility ' ; and even, ' The Mechanical Produc- 

 tion of Tastes and Colours.' The series finishes with ' The 

 Mechanical Origin of Heat and Cold.' To produce heat 

 it is necessary ' that the moving particles should be small'; 

 and ' agitation is requisite to heat ' ; in fact, a statement, 

 in language of the time, of modern views. In accounting 

 for the decomposition of bodies by heat, his words are : 

 ' It rather seems that the true and genuine property of 

 heat is to set amoving arid thereby dissociate the particles 

 of matter.' 



In spite of Boyle's numerous attempts to account for 

 natural phenomena in terms of matter and motion, his 

 modesty led him to make this statement : ' Having met 

 with many things of which I could give myself no probable 

 cause, and some things to which several causes may be 

 assigned, so differing as not to be able to agree in anything 

 unless in their all being probable enough;.! have often 



