NATURAL PHILOSOPHY. 85 



5.44 by Reich, 5.43 by Cavendish, and 5.56 by Baily. by means of the 

 torsion balance; and 6.55 by Airy, at the summit and bottom of a 

 coal-mine. 



ATTRACTION AND ADHESION. 



The phenomena of attraction and adhesion, as exhibited in solid 

 bodies, films, liquid globules, etc., have been investigated by Mr. Rich- 

 ard Norris, whose paper on the subject appears in the Proceedings of 

 the Royal Society, from which we extract a few experiments. These 

 Mr. Korris prefaces by reminding his readers that it has long been ob- 

 served that solid bodies floating on liquids modify the figure of the 

 surface of the liquid ; pieces of tinfoil or greased bodies depress the 

 liquid around them, whilst other bodies elevate it, giving rise to small 

 mounds of liquid bounded by concave lines ; likes attract likes, and 

 repel unlikes, etc. He states that the following experiments are 

 arranged to show that these effects of attraction are not peculiar to 

 floating bodies, and that the only requirement is that the liquid should 

 be associated with the bodies in which the movement occurs. 1. Let 

 two balls of sealing-wax, or other material of greater specific gravity 

 than water, be suspended by hairs in such a manner that they will both 

 be partially immersed in water to an equal extent, the points of sus- 

 pension being at a little distance apart, and the suspending hairs- con- 

 sequently parallel. When brought within the proper range, they will 

 attract each other in the same manner as the floating bodies. In 

 doing so they necessarily describe a small arc of a circle, of which the 

 suspending hair is the radius, and have, therefore, not simply moved 

 toward each other in a horizontal line, but have been raised to a 

 higher level. 2. Suspend movably, by means of a thread passing over 

 a pulley and a counterbalancing weight, a horizontal cork disc, from 

 the under surface of which a drop of water is hanging. On a support 

 beneath, formed by three upright pins, place a small piece of paper or 

 thin glass, on the surface of which there is also a drop of water. On 

 depressing the disc until the two drops of water touch each other, the 

 paper or plate will be instantly drawn up to it ; or, if the plate at the 

 bottom be heavier than the disc, the latter will be drawn down. 

 3. When a soap-bubble is allowed to fall on an ifregular surface, such 

 as a piece of lint or flannel, it maintains its spherical shape ; but if a 

 smooth surface, such as a sheet of glass, be brought into slight contact 

 with it, the wall of the bubble will be immediatelv attracted and flat- 







tened out upon it. In like manner, when two bubbles come in contact 

 by their convex surfaces and cohere, the cohering surfaces become flat- 

 tened, and the bubbles in a group cohere by plane surfaces. 



STEAM BOILER EXPLOSIONS. 



The following novel ideas respecting the explosion of steam-boilers 

 were given to the British Association, 1863, by Mr. Airy, the Astrono- 

 mer Royal. He said, that in considering the cause of the extensive 

 mischief done by the bursting of a high-pressure boiler, it is evident 

 that the small quantity of steam contained in the steam-chamber has 

 very little to do with it. That steam may immediately produce the 

 rupture ; but as soon as the rupture is made, and some steam escapes, 

 and the pressure on the water is diminished, a portion of the water is 

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