424 THE POPULAR SCIENCE MONTHLY. 



But in saying this I have no intention of denying that ozone is of 

 great importance in the atmosphere, for I am of opinion that it is. 

 It is the constant purifier of the atmosphere from all organic matter, 

 which passes into it and might accumulate. The air -would have 

 been long ago filled with the vapors of decomposition if it were not 

 for ozone, which oxidizes all that is oxidizable, if only time enough is 

 allowed for it, and too much is not expected at once ; for, generally, 

 the amount of ozone in the air is so small that it is consumed in 

 making its way into our houses, without disinfecting them, and we 

 can no more dispense with the greatest cleanliness and best ventila- 

 tion in our homes than we can essentially change the air in our rooms 

 by means of plants in pots and foliage. 



Some of my readers will perhaps ask in some disappointment, " In 

 what, then, does the hygienic value of plants and plantations consist? 

 Or do I mean to say that all the money spent by one and another on 

 a parterre of flowers in his house or on a garden, or by a community 

 for beautiful grounds, or by a state for the preservation of forests, 

 with the idea of promoting health, is mere luxury, without any hy- 

 gienic value?" These questions alter our standpoint, and I believe I 

 shall be able to show that even hygiene does recognize a sanitary 

 value in plants and flowers, in the laying out of grounds and planta- 

 tions, only it offers a different explanation from the ordinary one. 



I consider the impression which plants and plantations make upon 

 our minds and senses to be of hygienic value ; further, their influence 

 on the conformation of the soil, with which health is in many respects 

 connected; and, finally, their influence upon other qualities of the air, 

 than carbonic acid, oxygen, and ozone : among these may be men- 

 tioned, in passing, shade in summer, and decrease of wind and dust. 



It is an old observation, needing no demonstration, that the cheer- 

 ful and happy man lives not only an easier, but, on the average, a 

 more healthy life than the depressed and morose man. Medical men, 

 and especially " mad doctors," could tell us much of the great value 

 of a certain relative proportion of pleasurable and painful impressions 

 upon health, and how frequently some unfortunate position, an ab- 

 sence of pleasure, or too much of painful impression, is the cause of 

 serious illness. Man always tries, and has an irresistible need, to 

 balance painful sensations by some kind of pleasure or other, so that 

 often, in order to get himself into a tolerable frame of mind, or to 

 deaden his feelings for a time, he will have recourse to wine, beer, or 

 spirits, though he knows well enough that he will be worse afterward 

 than before. A certain amount of change and recreation is indispen- 

 sable, and, failing others, we seek them by injurious means. There 

 are, doubless, some unhappy and morbid natures who are always 

 discontented, to whom everything comes amiss, and whom it is im- 

 possible to help ; but the majority of men are easily pleased, find 

 pleasure in little things, though it is but a sorry life they lead. It 



