Spencer. — On Life. Ill 



It is not at all necessary to the perception of sound that the vibration 

 should be received by and traverse the ear. The ear itself is merely a 

 mechanism for augmenting and transmitting the sound, just as a relay in- 

 strument is used in long telegraph lines to increase and pass on the almost 

 exhausted cm-rent. Sonorous vibrations can traverse wood, water, metals 

 — in fact any substance which possesses the requisite degree of elasticity, 

 even the bones of the skull, for it is well known that in certain forms of 

 deafness the ticking of a watch held between the teeth is distinctly audible, 

 when its application to the ear produces no sensation. But the vibration of 

 sound can, by appropriate means, be rendered visible ; they can also be 

 counted, and we know precisely how many vibrations per second are 

 required to produce a note of any given pitch. But there are other modes 

 of motion which we are capable of perceiving through the medium of our 

 senses. If we take a piece of iron and hammer it on an anvil, after a time 

 the percussion produces motion amongst the molecules of the iron, and this 

 motion is perceptible to our senses — if we place a finger on the vibrating 

 iron we feel the vibrations, and say it is hot. If the hammering of our 

 supposed piece of iron be continued stronger and faster, or if it receive one 

 tremendous blow as from a Nasmyth hammer, the molecular vibrations 

 become so rapid that they are capable of setting in motion the particles of 

 the hypothetical luminiferous aether by which they are conveyed to the eye, 

 and we see them. This we term light. Together with the production of 

 light electrical phenomena are called into play, and the relationship 

 between heat light and electricity is so intimate that it too must be included 

 amongst modes of motion. All these then, — sound, heat, light, and 

 electricity, — are simply molecular vibrations which are perceptible by our 

 senses. 



As examples of the natural forces, I may mention gravitation, that force 

 which draws masses of matter towards each other ; — chemical affinity, that 

 force by virtue of which bodies of dissimilar nature unite to form compounds 

 of definite constitution ; — and cohesion, the power which holds the particles of 

 substances of a like nature in contact. The i^roperties of matter may be 

 considered as either general or special properties. The former include 

 impenetrability, extension, divisibility, compressibility, and inertia; the latter, 

 solidity, fluidity, tenacity, ductility, elasticity, hardness, transparency, and 

 many more. The question for our consideration is, can we relegate that 

 series of phenomena we term life to either of the foregoing categories ? 

 Before we attempt a solution, I will endeavour to explain to you a few of 

 the processes of life, and also something about the matter which exhibits 

 these processes. For life can by no means be dissociated from matter — 

 without a peculiar form of matter we never find life, without life we never 



