256 Scientifie Intelligence. 
tremity of the heiicontttdrpesile, the magnetic normal. The rule is 
placed horizontally and in an east and west direction, perpendicular te 
the magnetic meridian. In using it the magnet is made to approach 
the needle parallel with the sides of the rule. The distance at which 
it acts on the needle indicates its sphere of activity, as compared with 
any other magnet that may be operated upon. Not only different nee- 
dles may be thus compared, but the different poles of the same mag- 
net; and as the force diminishes as the square of the distance, the dif: 
ferent lifting forces of magnets of equal transverse sections may be 
deduced. M. de Haldat, with the same means, has experimented on ; 
the effects of interposing different media between the magnet and the 
needle ; and he finds no appreciable difference, whatever substance he 
used, or however great its thickness. This was true of iron as well as 
other substances. He has ascertained the singular fact, (an exception 
to the usual law of the propagation of these subtle fluids,) that the 
union of two magnets of equal intensity, although producing an in- 
crease of lifting force, does not increase the sphere of activity. The 
sphere of activity therefore cannot be enlarged except by adding a mag- 
net of greater intensity, and then will equal that of this stronger mag- 
net alone. This fact.is likewise confirmed by the magnetic phantom, 
in which the rays and characteristic curves are made more distinct and_ 
beautiful by the uniting of two magnets, but the extent of the figure, 
produced by the action, is no greater than with one. 
4. Calorific Power of the Light of the Moon ; ‘(A letter etter from M. 
Melloni to M. Arago, and Chemist, May, 1846. )—M. Melloni has shown, 
beyond a doubt, that the - rays of the moon are calorific to a slight ex- 
tent. It was done by concentrating the rays of the moon with a lens 
over three feet in diameter, upon his thermoscopic pile. The needle 
was found to deviate from 0°'6 to 4°-8 according to the phase of the 
moon. Numerous precautions had to be attended to so as to avoid all 
error arising out of currents of air, &c. 5 I 
5. On the Cohesion of Liquids and its effect upon the phenomenon ‘of 
Ebullition ; by F. Donny, (Annales de Chem. et de Phys., Feb. 1846, 
p- 167.)—These experiments disclose some very remarkable cireum- 
stances connected with the cohesion of the particles of liquids: They 
were undertaken upon the author’s observing that a syphon gauge con- 
structed by him with sulphuric acid, (perfectly free from air,) for the 
Purpose of testing the airpump vacuum, was useless; the acid remain- 
ing stationary, being sustained by the adhesion of the acid to the tube 
_ and the cohesion. between its own particles ;—and by means of these 
Ge oi in sustaining a column of sulphuric acid 
) four feet in’ ork oe even ina js ener -_ not- 
ee nt Ne 
