G4 



conditions, so the freezing point remains constant under similar 

 conditions. But if water be subjected to pressure or kept entirely- 

 undisturbed it can be cooled considerably below the temperature at 

 which it generally solidifies. A like result is said to follow if it be 

 exposed in fine capillary tubes. As soon as the pressure is removed or 

 the water disturbed, ice forms very rapidly, the water at the same time 

 increasing in temperature tiU the point at which it generally freezes is 

 reached. The heat then manifested, by an increase of temperature was 

 up to that time latent in the water. A very interesting experiment to show 

 that pressure affects the freezing of water was made by filling a cannon 

 ball (shell) with water, closing the opening and exposing it to a low 

 temperature. After a time the pressure produced by the formation of 

 ice was sutficient to break the ball. The pressure being relieved the 

 water froze so quickly that the portion of it which had been forced out 

 had not time to drop to the ground but formed a well defined, sharp 

 ridge of ice. 



A factor influencing the freezing of watery solutions is the nature 

 and quantity of the material dissolved. If these be gaseous the water 

 will generally freeze more readily, therefore, water which has boiled 

 requires a lower temperature than that from which some of the gases 

 have not been driven off by boiling. On the other hand solids held in 

 solution lower the freezing point. Since the sap of plants consists 

 of a watery solution of principally solid materials separated by the 

 cell walls into narrow channels or small drops — both factors retarding 

 freezing — we may look m this direction for the explanation of the fact 

 that some herbaceous plants can withstand several degrees of frost 

 without injury. 



Remembering that water is only a simple inorganic compound, and 

 reflecting upon its many properties and varied functions, not only 

 in nature but also in the arts, how it is made use of in the 

 steam engine, the hydraulic press, and the water wheel ; in the 

 laundry and the kitchen — its effects in the lakes and rivers — how it has 

 excavated monstrous caves and deep ravines — • its' aid to commerce and 

 its important offtces in the soil and the atmosphere, in plants and in our 

 own bodies — and then, when we notice how every property it possesses 

 seems specially designed to make this globe more perfect and to assist 

 in the working of the laws of nature, I am convinced that those who 

 reflect on these things must all feel a desire to study these laws more 

 thoroughly. 



