234 Intelligence and Miscellaneous Articles. 



decomposition of hypophosphorous acid by copper salts*. Hypo- 

 phosphorous acid is, like zinc, what is termed a reducing agent. It 

 precipitates certain metals from their solutions, and by a process of 

 deoxidation decomposes alkalies with the formation of phosphorous 

 acid and hydrogen. If this hypophosphorous acid be boiled with 

 the copper salt, nothing is perceived but the formation of metallic 

 copper and hydrogen gas ; but if the solution be gradually heated, 

 and the action arrested at a certain point, it can be shown that this 

 formation of hydrogen is preceded by the formation of a combina- 

 tion of hydrogen and copper, Cu 9 H, analogous to zinceethyle. The 

 part which this bears in the formation of the hydrogen is distinctly 

 shown by the action of acids, hydrochloric acid, HC1, for example, 

 upon it. This acid, which does not act upon metallic copper, im- 

 mediately decomposes this body, forming protochloride of copper, 

 *Cu 2 Cl, and hydrogen, HH. 



This hydride of copper has only a very ephemeral existence. It 

 is decomposed very nearly at the same temperature at which it is 

 produced, and its formation for this reason had long been overlooked 

 by chemists. We can hence readily comprehend that other com- 

 binations of this class may take place in the case of which the tem- 

 perature of formation and of decomposition may either coincide, or 

 so closely approximate to each other, that it may ever be impossible 

 to isolate the substance produced. This is probably the case in the 

 action of zinc. 



XXXV. Intelligence and Miscellaneous Articles. 



ON THE INFLUENCE OF THE EARTH'S ROTATION ON THE MOTION 

 OF A CONICAL PENDULUM. BY M. A. BRAVAIS. 



ON the 10th of February, 1851, 1 had the honour to notify to the 

 Academy, that the unequal duration of the vibrations of a right- 

 and left-handed pendulum appeared to me to be a necessary conse- 

 quence of the beautiful experiment of M. Foucault on the deviation 

 of the plane of oscillation. (See p. 197 of the preceding volume 

 of this Journal.) 



M. Arago having had the goodness to place the great meridian - 

 room of the observatory at my disposal, I was able to make the ex- 

 periments necessary to the testing of this point, with a pendulum 

 10 metres long ; and thus not only to confirm the predictions of 

 theory, but to do it with a degree of accuracy which I had not pre- 

 viously ventured to hope for. 



I applied two different methods, that of direct observation and 

 that of coincidences. In the direct observations, I observed the 

 duration of 900 to 1200 left-handed oscillations (from west through 

 south to east), and immediately afterwards the deviation of an equal 

 number of right-handed ones. The distance of the point of suspen- 

 sion from the centre of the weight amounted to from 10,187 to 

 10,197 millims. The observed duration was as follows : — 

 * See Ann. de Chim., 3rd series, vol. xi. p. 250. 



