Intelligence and Miscellaneous Articles. 167 



as to have the same temperature on all sides. The next morning 

 all the vessels were covered with a layer of ice of about 12 to 14 

 millims. thick ; and at the bottom and sides of the three iron vessels 

 there was a smooth layer of ice about 20 millims. thick, that on the 

 bottom being thinner. In the wooden vessel there was a layer about 

 2 millims. thick, and a few tufts of needles on the sides ; and on the 

 bottom there were a few isolated plates of ice 100 millims. long, 5 

 to 7 millims. wide, and 1 to 2 millims. thick, with other small plates 

 on the edges like the teeth of a saw. These experiments were re- 

 peated several times, and always gave the same result; that is, 

 the vessels were covered on the sides and bottom with a layer of ice, 

 the thickness of which varied with the conductibility and radiating 

 power of the vessel. 



To observe the formation of ice at the bottom of water, iron dishes 

 of about 5 centims. depth were filled with water and placed on a 

 freezing mixture of ice and salt. The temperature of the room was 

 + 15° ; and consequently there was no formation of ice on the sur- 

 face, but on the bottom. The congelation did not always take place 

 in the same manner. Sometimes needles formed at the bottom, 

 and gradually increased until the ascending force caused by their 

 lower specific gravity forced them to break loose and rise to the sur- 

 face. At other times the bottom was rapidly covered with a thin 

 layer of ice, sometimes marked with fine lines. 



To come to the formation of ice at the bottom of rivers. The 

 water at a temperature of 0° only loses heat on the surface by ra- 

 diation, or by contact with colder bodies. The earth at the bottom 

 and sides of rivers is a bad conductor, but water and ice are still 

 worse conductors. Ice being specifically lighter than water, always 

 swims to the surface when its ascending force is able to overcome its 

 adhesion to the bottom. It can also carry with it heavy bodies from 

 the bottom of the water. 



As the maximum density of water is at 4°, all large and tranquil 

 masses of water, and even those which have such a motion that the 

 layers are not prevented arranging themselves according to their 

 specific gravity, are at a temperature above 0° at the bottom of the 

 water, even when they are frozen on the surface. A pond at Nie- 

 derbronn, which is only a metre deep, was covered with ice at the 

 surface, while the water in the inside was + 3°, the temperature of 

 the air being — 1 1°. 



Large masses of water never freeze at the bottom ; and even when 

 ice does form, it becomes detached and rises to the surface. But 

 when water at 0° is in a vessel also at 0°, ice forms at the bottom as 

 well as at the surface. In order that ice may form at the bottom of 

 water, it is necessary that the lower layers be cooled to 0°, and even 

 a little more, that this cold water sink to the bottom of the river, 

 cool the sides, and finally find in the midst of the motion some- 

 thing at rest where it can exert its force of adhesion and crystalli- 

 zation. 



An obstacle placed in the current of water produces two different 

 effects. It either changes the direction of the liquid molecules 

 which strike against it, and gives them rotatory movements strong 



