March 15, 1877] 



NA TURE 



435 



Action on Frog's Eye of Specirujn of Oxyhydrot^en Flame. 



Initial EfTect. Final Effect. 



Yellow, near orarge... lise of 70 riie of 10 



Green yellow ,, 25 ,, 5 



Greea — low ,, 15 >> o 



Green — high ,, 15 ,, o 



Green — higher ,, 18 ,, 8 



Yellow green ,, 85 ,, 35 



Yellow M 80 ,, 40 



{To be continued.) 



SIR WILLIAM Gh VE ON THE RADIOMETER 1 



CIR WILLIAM GROVE described some experiments he had 

 *--' recently made with a modification of Crookes's radiometer. 

 After a few prefatory trial*, such as coa ing one-half of the bulb 

 with tinfoil and tlectrising it, which gave no notable results, he 

 devistd a method, shown in the accompanying sketch, by which 

 he could electrise the whole of the internal system. Four alu- 

 minium vanes, each blackened on one side, had metallic arms 

 and a metal point at their crossing that rested in a metal cup. 

 The latter was united to a platinum wire that passed through a 

 glass lube and was fused into it, the platinum wire protruding. 

 Lasily, the glass tube was fused inside the apparatus and her- 

 metically sealed, the end of the platinum 

 wire being exposed. The vacuum in this 

 apparatus was considered by Mr. Crookes^ 

 to be a"; perfect as in his radiometers gene- 

 rally, but Sir WiUam Grove doubted that 

 it was so. The following weie the results : — 



1 . With the faint light of a lucifer match 

 or of one or two candles, the vanes in- 

 variably turned the opposite way to the 

 normal, the polished .surface being re- 

 pelled. With a dark heat, as from an iron 

 shovel heated short of redness, ihey went 

 the normal way. These effects continued 

 for several days, but not permanently ; 

 the apparatus seemed to have leaked and 

 to have become sluggish and irregular. 



2. On electrising the protruding platinum 

 wire with a rubbed rod of glass or sealing- 

 wax, the vants rotated sometimes one way 

 and sometimes the other. 



3. On connecting the negative pole of a 

 Ruhmkorf's coil the results were uncer- 

 tain, but the positive pole caused the vanes 

 to rotate steadily, and its effect was even 

 better than that from light or heat. In 

 the dark the effect was very beautiful, as 

 the dark vanes moved through a phos- 

 phorescent glow. The total results were 

 considered by Sir William Grove to be 

 somewhat negative, but they tended to 

 show that all the effects were due to resi- 

 dual air. He suggested in explanation of 



the last experiment, that more electricity would escape from 

 the rough than from the polished faces of the vanes, as the former 

 presented a vast number of points. Consequently the n^ugh faces 

 would produce more disturbance of the gas in front of them, and 

 would themselves be more affected by the reaction than the 

 plane faces. The polished surfaces being repelled by luminous 

 heat is, however, very difficult of explanation. 



In his second notice Sir William Grove described some further 

 experiments he had made with Crookes's radiometers since the 

 last meeting of the club. He did not now entertain much doubt 

 that these movements are due to the effect of residual air. Mr. 

 Crookes had kindly made a second instrument for him, and the 

 one that he described at the last meeting, of which the vanes 

 were metallic and in metallic connection with a platinum wire 

 that protruded outside the apparatus, had been re-exhausted. 

 Both now act normally, the black faces of the vanes being repelled 

 by light and by heat. When the protruding wire is now elec- 

 trised by a Ruhmkorf's coil the effects that were previously 

 observed are altogether absent, there is not the slightest 

 luminosity round the vanes, and the current does not pass. 

 But although the current is now incapable of traversing the 



' Ab tract of two communications by the Hon. Sir William Grove, F.R.S., 

 to the Philosophical Club, May 18 and June 15, 1876. 



* Who kindly made it for me from my dcscriptioa. — W. R. G. 



small space of one-tenth of an inch that separates the vanes 

 from the glass, induction acts across it just as well as before. 

 This is shown by the readiness with which the vanes follow the 

 movements of a piece of rubbed glass or sealing-wax held near 

 the apparatus. It is therefore evident that the effects of attenu- 

 ation of air upon discharge and upon induction are not the same. 

 When attenuation has commenced and is increasing, the dis- 

 charge passes more and more rapidly, until it becomes a glow, or 

 according to the old theory of electricity, polarisation becomes 

 more and more readily subverted ; but a further attenuation stops 

 the discharge entirely. On the other hand, induction continues, 

 and appears to be in no way lessened by extreme attenuation. 

 These results cannot be accounted for by the old theory that 

 discharge is the consequence of subverted induction. 



It farther appears that a radiometer is a most delicate electro- 

 scope. By tilting it until the vanes touch the glass, the interior 

 of the glass may be e'ectrised, and it will then remain for days in 

 that condition. He had performed this operation eight days ago, 

 and the movements of the instrument by light or heat have been 

 thtreby wholly checked. Every endeavour has been made to 

 discharge or neutralise the electricity on the glass surface, as, for 

 example, by covering the exterior of the globe with tinfoil and 

 connecting this with the platinum wire, nevertheless the glass 

 remains charged, showing what a perfect insulator a good 

 vacuum is. ^ 



The above is a copy of the abstracts in the club book. They 

 are now further published, as some partial notices of them have 

 appeared in foreign journals. W. R. G. 



THE NORWEGIAN NORTH SEA EXPE- 

 DITION, 1876=* 



II. 



Researches relating to the Salt-ivater Fisheries. 



"D Y the side of the more strictly scientific researches it was 

 -^ also our intention during the expedition, if opportunity 

 offered, to give close attention to all the circumstances that 

 might stand in any connection with or throw any light upon our 

 most important salt-water fisheries. As I already during a 

 series of years had been engaged in the study of our fishtries, 

 the prosecution of these researches was committed to me. 



For this reason there was added to our other equipment 

 various fishing apparatus, as hooks and lines for deep-sea fish- 

 ing, and several sorts of drag-ntls with various sizes of mesh. 

 The use of such implements could, as a matter of course, only 

 be reckoned upon in good weather and with a pretty smooth 

 sea, which we, however, had promised ourselves might occur at 

 least now and then during our three months' excursion at the 

 btst season of the year. But the state of -the weather was un- 

 fortunately so utterly unfavourable during our whole expedition 

 that the employment of the apparatus we have referred to was 

 not to be thought of. For the same reason the apparatus for 

 measuring the velocity of the currents, exceedingly important in 

 the first place for the physico-meteorological researches, but 

 aLo for those with which we are now concerned, could not be 

 brought into use. During the few fine days we had in the 

 course of our expedition we were too near the coast for these 

 researches to have any special interest. 



Although the state of the weather thus laid insurmountable 

 obstacles in the way of the researches referred to, I have, how- 

 ever, during our expedition, been able to establish certain facts 

 which, in my opinion, are of no inconsiderable importance in 

 this direction, and will be of great use in guiding us in ihe con- 

 tinued practical scientific researches concerning our fisheries. 

 It is of these facts that I now proceed to give some details. 



It is ascertained by our soundings that off our coast there are 

 several fish-banks of whose existence there was no previous 

 knowledge, and on which a profitable fishery with bank vessels 

 may certainly be carried on during the summer months. 



The so-called " Storegg " (great edge) off Romsdal's Amt has 

 been from old times famous for its immeasurable richness in f sh, 

 and there has been an obscure tradition that it was not the only 

 point where such fishing could be carried un en a large scale, but 

 that there were to be found bimilar rich fish banks at manyothtr 

 points far out in the optn sea, "were man only fortunate enough 

 to fall upon them." The mystic account of the " Havbro " (sea 



' I m-y state that the electricity did ultimately become dissipated, but 

 not until several weeks had elapsed. — W. R G. \ 



* By Prof. G. D. Sars. From Chrisiiaaia Z^fi^'Wrt^^ of January 27. Con- 

 tinued from p. 414. 



