Dec. 9, 1886] 



NA TURE 



body, whereas among the summer herrings a large per- 

 centage have it behind the centre. In the immature fish, 

 however, the fin-centr; is generally anterior to the body- 

 centre. The anal and pelvic fins show a corresponding 

 difference in position. .As regards the pelvic fin, however, 

 this condition is limited to the adult and larger young 

 herring, the pelvic fin being found, like that of the sprat, 

 anterior to the dorsal fin in young herring below 60 milli- 

 metres in length. The pectoral fin varies very slightly in 

 its relative position on the winter and summer herring. 

 The relative basal length of both the dorsal and anal fins 

 conveys no indication of racial distinction between the 

 summer and winter fish. The dorsal fin is in all the 

 herrings generally longer than the anal ; only about i h per 

 cent, of the summer herrings, and 7^ per cent, of the 

 winter, having the anal fin longer than the dorsal. Further 

 details are given respecting the number of fin-rays, keeled 

 scales, circumstances of spawning, &c., but which scarcely 

 aft'ect the question of racial distinction. The inquiry, so 

 far as it has gone, tends to prove that there is no racial 

 distinction between the herrings found in the various 

 localities around the Scottish coast. Judging, however, 

 from the more backward position of the dorsal pelvic and 

 anal fins, the doubtfully smaller head, and the slightly 

 lesser size of the summer herrings, more minute inquiries 

 may indicate a slight difterence between the winter and 

 summer herrings. 



Mr. Brook reports on the herring-fishery of Loch Fyne 

 and the adjacent districts during 1S85, and under his 

 " Ichthyological .Notes " gives a short account of the rare 

 fishes met with during the ye.ir. 



Naturalists and fishermen alike have long felt the 

 absence of accurate information as to the spawning 

 period of fishes. In order to have a basis on which to 

 found further investigations, Mr. Brook has prepared a 

 provisional list of the spawning period of various food- 

 fishes. This list brings out the great lack of accurate 

 information on the subject, but gives an idea of the 

 opinions as to the spawning periods held by fishermen 

 and others around our coast. These opinions are in 

 many cases conflicting, and in most cases they will 

 require to be altered. Prof. Mcintosh contributes 

 an account of the work undertaken at St. .Andrews 

 since the last Report, including notes on the eggs and 

 young of fishes studied during the past year. Recently 

 considerable attention has been devoted by Mr. Wilson 

 to the development of the common mussel, and an 

 account of his investigations up. to the present time 

 will be found in the appendi.K. During the summer 

 and early autumn several attempts were made to fer- 

 tilise the eggs artificially at St. .Andrews. The early 

 stages of development were studied from ova obtained in 

 this manner, while the free-swimming embryos were 

 frequently obtained in pools amongst the mussel beds in 

 the Eden and in other localities. In the Board's last 

 Report it was mentioned that Prof. Greenfield had under- 

 taken to investigate the lower organisms met with in some 

 of our more important salmon-rivers. This investigation 

 has been advanced a step, and numerous forms have been 

 isolated and cultivated by the methods previously de- 

 scribed. 



Mr. Brook and Mr. Calderwood give the further results 

 of examination of the food of these " useful " fishes, the 

 herring, the cod, and the haddock. Mr. Calderwood also 

 sends notes on the Copepods of Loch Fyne, and on the 

 Greenland shark ; Canon Norman reports on a Crangon, 

 some Schizopoda, a member of the order Cumacea, new 

 to, or rare in, the British seas ; Dr. Stirling, on red and 

 pale muscles in fishes, and on economic products from 

 fish and corresponding vegetable products ; Mr. Hali- 

 burton, on the blood of Nep'irops noric^'aii/s ; Dr. John 

 Gibson, on physical observations made for the Fishery 

 Board in the Moray Firth during the autumn of 18S3. 

 Ten plates acconipmy the appendi.K. It is greatly to 



be regretted that the Board has not yet been able to 

 survey some of the fishing-banks, more especially those 

 which are supposed to extend along the western shores of 

 the Hebrides, and that the part of the Report dealing 

 with scientific work is not published separately. 



TBE ELECTRIC CHARGE ON THE ATOM 

 A LTHOUGH considerable attention has been given 

 ^*- of late to electrolysis and the subjects connected 

 therewith by English chemists, more especially since 

 the Helmholtz Faraday Lecture of 1S81, yet some of Prof. 

 Helmholtz's deductions from Faraday's experiments have 

 been curiously neglected. 



I refer more especially to the bearing of the facts on 

 the true nature of valency, and I purpose in this paper to 

 point out one or two fairly obvious consequences which 

 follow from the results of Faraday's researches, but which 

 have not, I believe, been stated before. 



Prof. Helmholtz has shown that it follows from 

 Faraday's experiments on electrolysis that while a 

 monovalent atom carries to the electrode one charge 

 of electricity a divalent atom carries two charges of 

 electricity. For instance, when we electrolyse potassium 

 chloride, we have each potassium atom delivering a 

 charge of electricity at the one electrode, and each 

 chlorine atom delivering an equal charge of electricity 

 at the other electrode, all monovalent atoms, carrying 

 with them an equal charge of electricity, which we 

 may call the unit charge. 



When, however, we electrolyse magnesium chloride, 

 we have two atoms of chlorine set free for one of mag- 

 nesium, and consequently while each chlorine atom 

 carries its unit charge with it, the magnesium atom 

 carries two units of electricity to the electrode. In 

 fact electrolysis proves that difterences of valency mean 

 differences in the electrical charge on the atom. All this 

 is so familiar to us now that I have perhaps repeated it 

 at unnecessary length. 



But we have many elements which vary in valency. 

 For instance, copper is capable of forming two series of 

 compounds, in one of which it is monovalent, and in the 

 other divalent, that is, in one of which the copper atom 

 carries one unit charge of electricity, and in the other 

 carries two units of electricity. 



We are able, then, under certain conditions to alter the 

 electrical charge on an atom, increasing it by some simple 

 multiple. 



There are therefore a special group of chemical reactions, 

 such as the oxidation of the cuprous salts, in which we have 

 not merely combinations between two or more substances, 

 or ordinarv double decomposition, but in which, besides 

 such changes, an additional electrical charge is given to, 

 or removed from, an atom. I think it follows from this 

 that all such reactions are of very special interest, and 

 deser\e careful study. 



For instance, take the case of the saturation of an 

 olefine by chlorine. We must look on this reaction from 

 one of two points of view. Either on the addition of 

 chlorine an additional charge is supplied to the carbon 

 atom, in which case by-products of less saturation are 

 probably formed ; or the carbon atom is already fully 

 charged, in which case the double bond is not merely a 

 shorthand statement of a possible reaction, but expresses 

 a physical fact. 



There is also another point worthy of note in connec- 

 tion with this addition of electricity to the atom. If we 

 take the case of the two copper chlorides— cuprous and 

 cupric chloride— we find that their heat of formation per 

 chlorine atom is not very dilTerent. Now it is well 

 known that the heat of formation of a salt approximates 

 to the heat of formation as calculated from the electro- 

 motive force developed when that salt is formed in a 

 voltaic cell. 



