PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 489 



a funnel at its top is inserted in the beaker nearly to the bottom. 

 A vial containing a few shot, to make its specific gravity the same 

 as that of fresh water, is tightly corked, and when placed in the 

 beaker barely floats just beneath the surface of the water. Now 

 by pressing in the cork slightly the size of this little glass boat is 

 made smaller, while its weight remains the same; yet its relation 

 to the water is changed because it is heavier than an equal volume 

 of water, and therefore it must sink to the bottom of the beaker. 

 Water, saturated with salt, is now poured through the glass tube, 

 and, having a greater specific gravity than the fresh water and the 

 little vial, it finds the lowest level in the beaker displacing the 

 fresh water and at the same time raising the vial, which now floats 

 midway in the beaker and on the line between the salt and fresh 

 water. This little experiment illustrates the action of a baloon 

 which does not rise of itself, but is pushed up by the heavier air 

 which is constantly displacing it. The difierence in temperature 

 afiecting density being then the cause of all motions of the air, 

 he had been inclined to believe it had more to do with the process 

 of breathing than was generally supposed. During the late heated 

 term he had observed many sickly children still in the nurse's 

 arms breathed with great diflaculty. He thought when the difier- 

 ence between the temperature of the air and that of the lungs 

 was greater, nature assisted the weak child in the process of 

 breathing. 



Dr. L. Bradley did not accept this doctrine. The action of the 

 lungs belong to the class of involuntary motions, but the strength 

 to move the lungs was a force generated in the body by means of 

 food. 



Dr. J. B. Rich said there was something in the position taken 

 by Dr. Howell: the involuntary action of the lungs did not do the 

 whole work; the coldness of the inhaled air and the warmth of 

 the exhaled air materially eflected the action of breathing. The 

 process required time. He had found when he had charge of the 

 physical training of many persons that with the aid of the vol- 

 untary muscle the process of breathing could not be carried on 

 with great rapidity for any length of time. 



The chairman said, with regard to ventilation, much that is 

 important remains untold. The law of the diflusion of gases is a 

 higher law than that of gravitation in some instances. This mat- 

 ter had been generally overlooked by inventors of ventilators. 

 He intended to say more on this subject at the next meeting. 



