518 Intelligence and Miscellaneous Articles. 



perpendicular to this axis is H. If V is the volume of the body 

 arid the angle of the field with the direction/, the moment of the 

 couple due to the action of the field is 



0= Y (f-f,) H 2 sin a cos a. 



It is readily seen that magnetization may be regarded as the 

 superposition of two other magnetizations — the one constant, /JX^ 

 parallel to the field and producing no couple ; the other, (/— /.,) H 

 cos a, connected with the body, and parallel to the direction of 

 greatest magnetization. This latter is sensibly constant for feeble 

 deflections. 



This is the case of a magnet which oscillates under the influence 

 of the Earth. If we take into account the induced magnetization, 

 we should strictly add to the rigid magnetization a magnetization in 

 the same direction (f—f x ) H proportional to the difference of the 

 longitudinal and transverse- coefficients. 



"We may add that for steel the mean coefficient of longitudinal 

 magnetization is much weaker than for soft iron, which greatly 

 tends to increase the importance of transverse magnetization. — 

 tes Rendus, May 5, 1886. 



ON AN INSTRUMENT FOE REPRODUCING AN INVARIABLE QUANTITY 

 OE ELECTRICITY. BY M. MARCEL DEPREZ. 



The object of this instrument is to reproduce readily and under 

 any given conditions of temperature and pressure the unit quantity 

 of electricity which is known as a Coulomb. 



It consists of a U-tube the two limbs of which end in glass bulbs 

 the volume of which is far greater than that of the cylindrical parts, 

 the whole being hermetically sealed. One of the bulbs and the 

 corresponding limb is completely filled with water acidulated by 

 phosphoric acid ; in the other limb it is filled with air at a definite 

 pressure as well as the bulb in which it ends. In the branch filled 

 with liquid are four platinum wires facing each other in pairs, two 

 at the top of the bulb and two others in the cylindrical part a little 

 below the lowest point of the bulb. If an electrical current is 

 passed through these latter, water is decomposed, and the detonating 

 gas arising from this decomposition accumulates in the upper bulb, 

 while the liquid driven into the second limb ascends in this, 

 compressing the air in the second bulb. If we take care to note 

 the point of departure of the column of liquid in the second limb, 

 which is divided into parts of equal capacity, as well as the point 

 at which it stops when the current is suppressed, we have all the 

 elements necessary for knowing the quantity of electricity expended 

 in producing the detonating mixture. It is readily seen that, if the 

 volume of this liquid measured by the rise of the liquid in the 

 second limb is constantly the same, the quantity of electricity 



