7 i8 THE POPULAR SCIENCE MONTHLY. 



find many substances which are apparently identical in composition, 

 but which possess diverse qualities. Certain conditions are requisite 

 to produce different states of the same compound. If these condi- 

 tions are not fulfilled, the required combination is not made. With 

 the cannibal our equation of the conservation of force would require 

 a small term to represent the mind and soul, but a comparatively 

 large one, it may be, to account for that stress of the particles, so to 

 speak, which manifests itself as life. The source of the physical 

 energy is the sun's heat. Looking, therefore, at the problem of life 

 and mind from a' purely scientific point of view, we seem to require 

 a source from which can come the principle of life, and which can 

 create moral and intellectual growth in suitable soil and under fit- 

 ting conditions. In the case of the energy derived from the sun's 

 heat we have a cycle of operations in which there is no annihilation 

 of force. If we grant that there is a source of life and mind inde- 

 pendent of mere chemical change produced by the sun's heat, and 

 if we adhere to the notion of the conservation of force applied to this 

 principle of life and mind, we are led to adopt the idea of a cycle of 

 operations in which there is no annihilation of spiritual force. The 

 doctrine of the existence of the spirit after physical death seems to 

 me not to be foreign to the scientific ideas of the conservation of 

 force, which have now obtained such complete supremacy in the sci- 

 ence of physics ; or to the doctrines of Darwin, which are accepted by 

 so large a body of eminent naturalists. Without the sun there would 

 be an annihilation of force. When energy is dissipated, we find the 

 sun exalting it again by processes which we cannot completely fol- 

 low. The idea of a great source of life and mind, the prototype of 

 our physical sun, which sets in motion a vast scheme for the survival 

 of the fittest, and the exaltation of energy in vast cycles, is not 

 inconsistent with the doctrine of the New Testament, and seems to 

 be required in a philosophical theory which shall endeavor to account 

 for the differences in that great spiritual world which are continually 

 suggested to the human mind by the various types of mental growth. 



THE FIEST "POPULAR SCIENTIFIC TEEATISE." 



By Professor S. P. LANGLEY, 



OF THE ALLEGHENY OBSERVATORY. 



QfOME one" has said that there is nothing in all the world of com- 

 ^ mon places which was not once a novelty, and born from the 

 conception of an original mind. The idea that science is not for the 

 professional student only, but that every one will take an interest in 

 Us results if they are only put before the world in the right way 

 this notion which has now produced a literature of its own even 



