60 PART II.- SOME IMPORTANT METHODOLOGICAL TERMS. 



substance was known as phlogiston. All combustible bodies were to be 

 regarded, therefore, as compounds, one of their constituents being 

 phlogiston: their different natures depended partly upon the proportion 

 of phlogiston they contain, and partly upon the nature and amount of 

 their other constituents. A body, when burning, was parting with 

 its phlogiston; and all the phenomena of combustion the flame, heat 

 and light were caused by the violence of the expulsion of that sub- 

 stance. Certain metals as, for example, zinc could be caused to burn, 

 and thereby to yield earthy substances, sometimes white in colour, at 

 other times variously coloured. These earthy substances were called 

 calces, from their general resemblance to lime. Other metals, like lead 

 and mercury, did not appear to burn ; but on heating them they gradually 

 lost their metallic appearance, and became converted into calces. This 

 operation was known as calcination. In the act of burning or of calci- 

 nation phlogiston was expelled. Hence metals were essentially compound: 

 they consisted of phlogiston and a calx, the nature of which determined 

 the character of the metal. By adding phlogiston to a calx the metal 

 was regenerated. Thus, on heating the calx of zinc or of lead with coal, 

 or charcoal, or wood, metallic zinc or lead was again formed. When a 

 candle burns, its phlogiston is transferred to the air; if burned in a 

 limited supply of air, combustion ceases, because the air becomes satu- 

 rated with phlogiston." (E.Thorpe, History of Chemistry, vol.1, pp. 71-72.) 



Lavoisier's theory that in combustion substances combine with 

 the oxygen of the air the very reverse of the assumption of 

 the phlogiston hypothesis that substances lose in combustion- 

 was the product of a more advanced age. 



The very ground we tread on has an immeasurably richer 

 meaning for the man of science than for the uncultivated: 



"Turn up a sod of earth in a pasture in winter, and at first sight it 

 seems to consist of two well-marked portions, a living and a dead one 

 the green grass above and the black soil beneath it. But look closer 

 into the mass, and what then do you see? A whole network of living 

 beings. Matted roots of grass, just as much alive as the green blades 

 above, spread and interlace themselves through the seemingly dead portion. 

 Bulbs of bulbous buttercup, of orchids, of garlic, lie hidden in it every- 

 where. Root-stocks of plantain, of chervil, of pimpinel, of daisy, are 

 knotted among its clods. Gaze closer still, and you will see that it is all 

 full of tubers or stocks of lesser weeds, in their dormant condition, all 

 ready to spring afresh at the first breath of April. How the endless 

 bulbs and corns and tap-roots manage to stow themselves away in so 

 small a space is to me a perpetual mystery ; in winter you hardly notice 

 the little potato-like pills of the lesser celandine, but in spring the plants 

 cover the ground with their golden blossoms, to be succeeded in due course 

 by the spotted orchid, the buttercups, the centauries, the hawk-weeds, 

 and all the countless flowers of July and August. They are packed as 

 tight as sardines in a tin. As for the seeds of small annuals they lurk 

 there by the thousand; sift out a little of the soil, and plant it in a pot, 

 and, hi presto! to your surprise, weeds will spring from it in incredible 

 numbers. The whole mass teems with dormant germs innumerable. 



"It is the same with animals. You think of this soil as dead; but it 

 is undermined by rabbits, rats, moles, and lizards. It swarms with in- 

 vertebrates. LarvaB of tiger beetles lie in wait in its crannies; grubs 

 and worms without end find a living in its hollows. Woodlice and petty 

 snails lurk under every stone; centipedes and wire worms crawl through 

 its interstices; testacella pursues earthworms as the ferret pursues the 

 rat ; a whole underground fauna lives and moves and has its being in 

 that seemingly dead congeries. Turn up a handful of earth, and examine 

 it with a pocket lens ; you will find it alive, like an ant-hill, with endless 



