GRAVITY AND LEVITY OF GASES. 255 



tained by the whole mass, at the centre of gra- 

 vity at the bottom, as it is called : (a centre at 

 the bottom!!!)* 



The error of confounding the attributes of 

 gases with those of liquids, and of liquids with 

 those of solids* is not more striking than the 

 fashion which prevails, of confounding pressure 

 with resistance, power with capacity the ca- 

 pacity which some bodies possess, of receiving 

 power through the medium of participation 

 from other bodies, with those which possess it 



* The centre of gravity is supposed to be that point in any 

 body, about which all its parts are equally balanced, or kept 

 in equilibrio. In regular and homogeneous solids, this point 

 is situated at equal distances from the extremities. In irre- 

 gular bodies, however, which possess unequal degrees of den- 

 sity, this point, or centre, as it is called, instead of being 

 situated in the middle of the line, is often more on one side 

 than the other ; the point of suspension altogether depending 

 on the equality of the matter which subsists on one side, with 

 respect to the other. " 1. The pressure of fluids is in propor- 

 tion to the base, and perpendicular height of the fluid, what- 

 ever be its form or quantity. 2. The pressure upon the 

 bottom of a conical vessel, is equal to the pressure upon the 

 bottom of a cylindrical one, of the same base and height. 

 3. The pressure of a fluid upon any indefinitely small part of 

 the sides of the vessel which contains it, is equal to the weight 

 of a column of the same fluid, whose base is the part pressed, 

 and whose height is the distance of that part from the surface 

 of the fluid." Enfuld. 



