250 Mr. W. H. Preece. Effects of Temperature on [May 24, 



alumina in being a sesquioxide, but is at once distinguished as it does 

 not afford an alum-like double sulphate as do alumina and its homo- 

 logues, and has comparatively little in common with that group, save 

 the tendency to form highly basic salts. Nilson and Pettersson,* 

 admitting this, maintain that beryllium is a leading member of another 

 group of triads, which includes the rare earth-metals scandium, 

 yttrium, lanthanum, didymium, terbium, erbium, &c. The recent 

 spectroscopic evidence above referred to is opposed to this contention, 

 as the spectrum of beryllium is stated to be wholly unlike the spectra 

 afforded by the rare earth-metals with which it is classed in the memoir 

 above cited. If, then, beryllium does not find a place in the two known 

 families of metallic triads, or pseudo- triads, it must stand alone ; and 

 in any case as a triad it is outside Mendeleef 's classification. But if the 

 atomic weight of beryllium be 9'2, according to my result, the metal is 

 a diad and the symbol for its oxide is BeO. It is, therefore, the first 

 member of Mendeleef's second series of elements. This position 

 is quite in accordance with the spectroscopic evidence obtained by 

 Professor Hartley, from which he concludes that " beryllium is the first 

 member of a diad series of elements, of which in all probability calcium, 

 strontium, and barium are homologues." 



III. " The Effects of Temperature on the Electromotive Force 

 and Resistance of Batteries. II." By William Henry 

 Preece, F.R.S. Received May 21, 1883. 



In the discussion on my previous paper read on February 22, 1883, 

 it was suggested that I should continue the observations on the 

 influence of temperature to the case of secondary batteries. I am 

 indebted to Mr. Tribe for one of his cells made so as to fit my 

 apparatus, and charged at different times with solutions of various 

 degrees of saturation. 



The negative element of this cell consisted of pure peroxide of lead 

 in the form of a plate 4 inches square carried in a grooved frame, from 

 one end of which projected the necessary conductor. This element 

 was placed between two plates of finely divided lead likewise 4 inches 

 square. These were joined together, and formed the positive element 

 of the cell. Each half of the positive plate was about a quarter of an 

 inch distant from the negative, and all three plates were encased in a 

 thin specially prepared fabric. The elements were contained in a 

 leaden case, and the liquid was sulphuric acid of the strengths given 

 in the various experiments. This cell was placed inside the cylindrical 

 copper vessel used in the previous experiments, and precisely the 

 same method of observation was adopted. The results are given in 

 * " Proc. Roy. Soc," vol. 31, p. 50. 



