THE INFLUENCE OF LIGHT ON LIFE. 253 



the water, is due to this marvellous power of light, for from what 

 we have just seen it seems reasonable to conclude that the sun is 

 continually destroying the germs of disease which exist around us. 

 No doubt the " sun bath," which I have been told is sometimes 

 resorted to in diseases of the lungs, is found advantageous for such 

 reasons as have just been given. It would be interesting to com- 

 pare the state of health of a community during a season of dull 

 and rainy weather with the state during a time of sunshine, as, 

 other things being equal, we might well expect to find our conclu- 

 sions as to the sun's beneficial influence confirmed by such a 

 comparison. 



An effort has been made in this paper to confine our attention 

 to the action of light as it directly influences the vegetable and 

 animal world, and to avoid an extension of the subject to the 

 influence of light upon other phenomena in the world of Nature. 

 Although its influence upon other forces and matters is of great 

 importance in an indirect manner in affecting plant and animal 

 life, still our subject is sufficiendy complete in itself without refer- 

 ring to them here ; at any rate, it is sufficiently large for one 

 evening's consideration. We have gleaned the various particulars 

 here given from many writers, as well as from common observa- 

 tion, and have taken some pains to confirm, from as reliable 

 sources as possible, the different experiments and results which 

 have been quoted. 



We have seen that almost the whole vegetable kingdom 

 requires, as absolutely necessary to existence, a sufficient supply 

 of light ; that animals are largely dependent, in a direct manner, 

 upon the same subtle influence, if, indeed, not also as dependent 

 upon it as plants; that man's physical and mental parts rebel 

 against the loss or absence of light, and are influenced in various 

 ways by its alteration ; and that the germs of disease which might 

 multiply beyond all knowledge are kept in check and subjugated 

 by the same friendly power. 



When we focus all these facts to a point, we feel inclined to 

 repeat the dying words of Goethe and ask for " more light," and 

 we are almost forced to recognise, in wide streets, large windows, 

 and plenty of sunshine and fresh air, a method or plan by which 

 Nature will help us most effectually to preserve a sound mind in a 

 sound body. 



