36 J. W. SLATE i;, ESQ., F.C.S., F.E.S., ON 



these pliysieal forces by their inauifestatious ; but we cauiiot 

 measure life by its manifestations. We can measure light 

 with great accuracy. We can compare one source of light 

 with another, and thus ascertain the luminous power of the 

 sun, of Sirius, of an arc-lamp, a glass lamp, a gas burner, 

 a candle, or an aurora bcn-ealis. We can show liow many 

 candles Ave should have to group together for their united 

 radiance to equal that of the sun. 



.5. In like manner we can measure lieat. We can find the 

 temperature required for melting any of the metals or for 

 boiling or evaporating away an}^ liquid. We can deter- 

 mine the quantity of heat which can be obtained, for instance, 

 by burning one ton of coal, of any determined composition. 



6. We can measure the power of a magnet, or of the electric 

 current produced by a dynamo, or by a galvanic battery of 

 some known construction. Most easily of all we can measure 

 mechanical poAver, or the motion Avhich it produces. 



7. But can Ave make any similar determination or measure- 

 ment Avith life? Can Ave, for instance, say Avhether there is 

 more or less life in a child or in a groAvn man, in a microbe 

 or in a whale, in an ox or in an oak tree ? Some of these, 

 and of many similar questions Avhich might be framed, 

 strike us at once not merely as unansAverable, but as absurd. 



8. You might, perhaps, say that there is more life in a man 

 than in a hedgehog. The man Avill IIa'^c longer, travel faster 

 and further, and exert more poAver in various directions than 

 can the hedgehog. He is a greater Aveight of living matter 

 — a point Avliich some people take as a standard. But 

 give the man a score of Spanish flies, and he Avill die in 

 torment. Give the hedgehog a similar dose and he Avill eat 

 them Avithout injury, and in his manner he Avill ask for more. 

 In short, his life resists and overcomes an agency Avhich des- 

 troys the life of man. 



9. We might, perhaps, fancy so swift, poAvcrful, and heaA-y 

 an animal as the African buffalo must contain more life than 

 a man. Not so; let man and Imftalo be each bitten b}^ a 

 Tsetse fly. The buffalo will shortly perish, hut the man 

 Avill experience no more incouA^enience than he Avould from 

 the bite of a gnat. 



10. Or again Ave might thhik that the quantity of life in an 

 ox would be almost immeasurably greater tlian that in the 

 spore of a microbe. Yet the sport' Avill resist degr(jes of cold 

 and heat much more than s\i(HciL'iit to kill the ox. 



11. We see further dilhculty in tinding a measure for lite if 



