4 -68 THE POPULAR SCIENCE MONTHLY. 



accumulation of pictures and records which -we would gladly eliminate 

 from the stock material of dreams ; but much may be done to improve 

 the store as a whole by feeding the mind with wholesome and healthy 

 thoughts and impressions. He who makes it a rule through life be- 

 ginning early in youth to take care that what he puts away in his 

 mind and accumulates is, as far as may be possible, a treasure of pure 

 and good materials, will do much toward making the dreams that haunt 

 his sleep in the later years of life not only tolerable, but, so far as 

 night-thoughts can subserve any useful or beneficial purpose, improv- 

 ing. There can be no question that pleasant dreams sometimes afford 

 relief to the mind, especially when they occur on awaking, or when 

 they blot out the disagreeable impressions of the day, and facilitate 

 the process of passing into a state of natural and complete sleep. Such 

 dreams do not last long, and are seldom so intense as to distress the 

 faculties. There is always a danger, in light sleep, of the senses being 

 partially awake to surrounding impressions, and making them the pegs 

 on which to hang a dream. It is, therefore, important to secure the 

 most peaceful and negative conditions for sleep. Dreams are often 

 made by the externals of the sleeper. To avoid this contingency, the 

 sleeper should train his senses to disregard the external when compos- 

 ing himself for sleep. This is not difficult to do if the mind is set 

 resolutely for a few nights in succession to shut out or ignore the im- 

 pressions that strive to attract it through either or all of the senses. 

 It is happily not required of us to know the way in which we accom- 

 plish all the acts we perform ; and, in respect to some, it is better not 

 to be too curious concerning the means if we gain the end. In regard 

 to dreams and the making of dreams it will, however, be found an 

 advantage to be fairly well-informed. Gentlemaii's Magazine. 



SANITARY RELATIONS OF THE SOIL* 



Br Dr. MAX VON PETTENKOFER. 

 II. 



WATER plays quite as important a part in the soil as air. Obvi- 

 ously, no organic* life, no organic change, can be conceived of 

 without water ; and we ourselves consist three parts in four of water. 

 Therefore it may be inferred that change in the moisture of the soil 

 must have a certain influence on its organic and organized constituents, 

 and on the organic life within it. Two degrees of moisture in the 

 soil may be especially distinguished : one in which air and water both 



* An address delivered before the Association of German Naturalists and Physicians, 

 at Salzburg, September 18, 1881. 



