NATURAL PHILOSOPHY. 115 



medan, Overrocs, is confirmed by all modern science, that the sum 

 total of force in the world is ever the same, though it is parted among 

 myriads of individuals, who draw from a common fountain their requi- 

 site supplies. 



The body that we have to-day is not the body we had yesterday ; we 

 shall change it again before to-morrow. In the course of a year a 



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man requires a ton and a half of material that is, nearly twenty times 

 his own weight to repair his wasting organs, and to discharge his 

 vital functions. In that short space of time, the human family aloue 

 casts into the atmosphere 1,800,000,000 of tons, and we are but a 

 little fraction of the vast aggregate of animal life which all in its 

 proper proportion is doing the same thing. 



From nature, which at this point of view presents us such an en- 

 chanting picture, let us turn to ourselves. Physiology rivals Natural 

 Philosophy in the splendor and profound interest of its discoveries. 

 We tremble on the brink of detecting the interior constitution of man. 

 Will you hear me patiently while I give an example of what I mean ? 

 No event has ever taken place in the world without spontaneously 

 leaving a recoverable impression of itself. The hand that wrote those 

 words has cast its shadow on the paper. A century hence, if the 

 paper should endure, that shadow might be made visible to the eye. 

 But moralists say, " What is more transitory than a shadow?" They 

 find in it an emblem of things of a fleeting nature. When the light, 

 or the object that has obstructed it, is withdrawn, the shadow "ileeth 

 away and continueth not.' 1 A sundial, that has been telling the hours 

 of the day, presents an unblemished surface when evening comes. 

 Each morning it is ready for its task. The traces of the past seem all 

 to have disappeared, but in truth they still exist, buried in the marble 

 or the metal out of which the dial is made. 



They who have visited ihe dark rooms of photographers know very 

 well what I mean. The portraits of our friends, or landscape views, 

 may be hidden, and invisible to the eye, but ready to make their appear- 

 ance as soon as proper means are resorted to, such as heat, or vapor of 

 mercury, or sulphate of iron, or pyrogallic acid. Shadows are not such 

 transitory things as men commonly suppose. In the case of photogra- 

 phy, we happen to know the proper means for development. The 1'act 

 of chief interest to us is the imperishability of the primitive impression. 

 A spectre is concealed on a silver or glassy surface, until by our necro- 

 mancy we make it come forth to the visible world. Upon the walls of 

 our private apartments, where we think that the eye of intrusion is alto- 

 gether shut out, and our retirement can never be profaned, there exist 

 the vestiges of all our acts, silent but speaking silhouettes of whatever 

 we have done. Can we siy that among those phantoms there are not 

 some on which we should be reluctant to have the cunning chemist try 

 his art, and leave them, as the photographers say, fixed : some from 

 which we should dread to hear the demand of the phantom of Endor, 

 " Why hast thou disquieted me to bring me up ? " 



If men were sure that their most secret doings were at such a risk 

 would not the world be better than it is ? A sunbeam or a shadow can- 

 not fall upon a surface, no matter of what material that surface is com- 

 posed, without leaving upon it an indelible impression, and an impression, 

 which may, by subsequent application of proper chemical agents, be 



