50 Mayoiv 



suppose, on being exposed to cold. For nitro-aerial 

 particles derived from the fire abound in boiling water, 

 and these when they cease to move on exposure to 

 cold no longer agitate the aqueous particles but fix 

 and freeze them. For the case here does not seem to 

 be very different from that of glowing iron being 

 plunged into cold water, for the iron, cooling rapidly, 

 becomes more rigid and so to say firmly frozen. And 

 indeed in my opinion frozen water differs from 

 hardened iron chiefly in this, that the branching 

 particles of the iron adhere firmly to each other as 

 though they were joined by clasping hooks, so that 

 the nitro-aerial spicules are more closely interlaced 

 with them. 



Hence too the reason is obvious why soil that has 

 been bound fast in the ice of winter becomes more 

 fertile in the following spring. Doubtless the nitro- 

 aerial particles from which when closely fixed in its 

 structure the freezing of the soil results, produce when 

 set in motion afterwards by the warmth of spring that 

 effervescence in the bosom of the earth to which the 

 generation of all-fertilising nitre and the growth of 

 plants are due, as is shown elsewhere. 



Further, that water is frozen by nitro-aerial particles 

 fixed in it seems also to be confirmed by the fact that 

 when frozen it is rarified and expanded. 1 am aware 

 that the ingenious Descartes gives a different explana- 

 tion of the rarefaction of frozen water. In fact that 

 eminent man supposes that the aqueous particles when 

 less disturbed by subtle matter cease to move and 

 become somewhat curved, from which it results that 

 they cannot then contract themselves into so narrow a 

 space as before, when the subtle matter having power 

 enough to bend them as it pleased was always adapting 

 their forms to the measure of the places in which they 



