2 5 2 



NATURE 



[July 13, I ! 



an experiment in which the external resistance was 1 ohm, 

 and the internal o'5S ohm, the E.M.F. sank in forty-five 

 minutes from 225 to v^z, but after being disconnected 

 for thirty minutes, it was found to have risen to 1 -96, and 

 after eighteen hours' repose it had actually risen to 1 98 

 volts. These observations were made many times in 

 succession during the course of the experiment, which 

 lasted six days. 



With twenty times the external resistance, the diminu- 

 tion of electromotive force was much slower ; but after 

 discharging three days, the fall was more pronounced, 

 and the rise on repose very apparent. 



With 100 ohms resistance, the electromotive force varied 

 very little for three days. 



It is more difficult to obtain satisfactory chemical evi- 

 dence of a quantitative character. It is clear that as 

 chemical examination means the destruction of the sub- 

 stances, the same plate cannot be analysed in two con- 

 secutive stages. Nor can two plates be easily compared 

 with one another, although they have been formed under 

 the same circumstances. Even the same positive plate, 

 during or after discharge, presents to the eye very different 

 appearances in different parts. To a certain extent we 

 obviated this difficulty by cutting the plate in two, longi- 

 tudinally, analysing the one half at once, and allowing 

 the other to repose for a given time before examining it 

 for peroxide of lead. 



As to the estimation of peroxide in the presence of 

 metallic lead, we finally adopted as the best method 

 that of reducing it by means of oxalic acid, although we 

 were not certain that the whole amount is obtained in this 

 way, even though the solution be kept hot for a consider- 

 able time. 



By this method many chemical examinations were 

 made of the positive plate. The results are as follows : — 

 First of all, when the external resistance did not exceed 

 20 ohms, the peroxide of lead was generally visible in 

 patches, and its presence was demonstrated and approxi- 

 mately measured by various chemical tests. On repose, 

 the quantity of this peroxide visibly diminished, and in 

 the majority of instances the chemical analyses also 

 showed a smaller amount. In all cases sulphate of lead 

 makes its appearance early in the action, and gradually 

 increases in quantity, becoming finally the only product 

 of the discharge. 



The deposit on the negative plate shows the presence 

 of nothing but sulphate of lead in addition to the un- 

 changed peroxide. At the conclusion of the action, we 

 have always found more or less of this substance unal- 

 tered. Thus, as one instance, after a discharge lasting 

 five days, and approximately complete, we found that 

 only 68 per cent, of the deposit was lead sulphate. 



We conclude therefore that the chemical action of the 

 discharge is essentially what is expressed by the following 

 theoretical formula : — 



PbOo I H 2 SOj I H 2 S0 4 I Pb=PbO | H 2 | H„S0 4 i 

 PbS0 4 , 

 which becomes 



PbS0 4 I H 2 I H 2 I PbS0 4 . 

 This reaction is, however, sometimes complicated by the 

 formation of a small amount of peroxide of lead on the 

 positive plate. We believe this to be due to the oxidation 

 of sulphate, an action which was explained in our last 

 paper. 



Another conclusion has reference to the resuscitation of 

 power observed on repose. This is not due to any purely 

 physical action but is a necessary consequence of the 

 formation of Pb0 2 on the positive plate. As sooner or 

 later the result of the action becomes solely PbSC> 4 , this 

 temporary formation of peroxide does not seriously affect 

 the quantity of electrical force that may be regained from 

 the accumulator, but it does affect the evenness of its 

 flow. The flow is more regular if the discharge be made 



slowly, but in that case the loss on the negative plate 

 from local action will probably be greater. 



As to practical conclusions, we may note — 1. Although, 

 as stated in our paper of March 9, the most economical 

 arrangement for the initial charging of the cell is to 

 " make the red lead to be hydrogenated much smaller in 

 amount than that to be oxidated," yet, as foreshadowed 

 in the same paper, this arrangement is not desirable for 

 the discharge of the cell. Nor is it for its subsequent 

 charging, since, as will have been seen, the substances to 

 be acted upon are now very different. On the negative 

 plate there will be the sulphate of lead produced by the 

 discharge, plus sulphate of lead produced by local action, 

 together with more or less unaltered peroxide. On the 

 positive plate there will be the sulphate of lead produced 

 by the discharge, together with excess of lead, if any. 

 Unless, therefore, the peroxide of lead unacted upon is 

 allowed to be very considerable, the quantity of lead 

 compound on the two sides ought to approach equality. 

 2. Care should be taken that sulphuric acid is in sufficient 

 excess to allow of there still remaining some of it in solu- 

 tion after all the available lead has been converted into 

 sulphate. If it is removed and only water is present, an 

 oxide or hydrate will be produced with probably some 

 serious consequences to the cell. 



J. H. Gladstone 



July 3 Alfred Tribe 



ON THE DEVELOPMENT OF THE CROCO- 

 DILIAN SKULL 

 'THE most striking thing in the development of the 

 *■ Crocodile is the structure of its visceral arches, and 

 especially those that form the jaws and the hyoid or 

 lingual arch. 



(a) Endoskeletal Parts of tlic Upper Jaw.— Inside the 

 massive outer bones of the upper face, or maxillaries and 



2><J- C 



Fig. I. 



X/A 



Fig. 1 —Upper pan of mandibular and hyoid arches, outer view of second 

 stage (Alligator missisipeusis), I J inch long. an. auditory capsule (in 

 outline): q. quadrate cartilage ; ot.p, it* otic process; a.J>. ascending 

 process ; /g.c, pterygoid cartilage ; <; e, condyle of quadrate ; mk, 

 Meckel's cartilage : ar.c. condyle of articular region of mandible ; f.hy, 

 pharyngo-hyal ; city, epi-hyal ; i.hy, inter-hyal; c.hy, cerato-hyal. 



jugals, there are the more delicate palatines, trans- 

 palatines, and pterygoids. These are formed in a mem- 

 branous tract of the palate, and but little cartilage, such 

 as is seen in fishes, makes its appearance. 



The pterygoids assist the palatines and maxillaries in 

 forming the " hard palate " or secondary floor to the nasal 

 passages, just as in the Ant-bear, Tamandua, and some 

 Cetacea amongst the Mammalia. This hard palate is 

 not seen in Snakes, Lizards, and the smaller Tortoises, 

 but is developed in some degree in the large Turtles. It 

 is but little developed in Birds ; for in them only a few - 



