356 



NA TURE 



[September i6, 1909 



A Large Group of Sun-spots. — Despite the fact that 

 we are now drawing near to a sun-spot minimum, the solar 

 disc has, during the past fortnight, exhibited an extensive 

 group of spots. An observation on August 28 showed a 

 bright patch of faculae some distance south of the equator 

 on the eastern hmb, and on the following day a small 

 spot was observed near the limb to the north of this. 

 Observations on September 6 showed that there was a 

 group of small spots in about the latitude of the previously 

 observed facute, and this developed until, on September 11, 

 it was a diamond-shaped group, of medium-sized spots, of 

 which the longest diagonal was about one-sixth the length 

 of the sun's diameter; each of the four main spots was 

 surrounded by a number of smaller nuclei. 



The Transv,\al Observatory. — From a note in the 

 Observatory {No. 413, p. 369) we learn that the Transvaal 

 Government, on behalf of the Government observatory, 

 has accepted the gift of a photographic astronomical 

 telescope from Mr. Franklin Adams. The triple-objective 

 is of 10 inches aperture, and made by Messrs. Cooke and 

 Sons. Two guiding telescopes, each of 6 inches diameter, 

 accompany the main instrument. The telescope is erected, 

 and is to be employed mainly in assisting Prof. Kapteyn, in 

 his studies of the construction of the sidereal universe, by 

 securing photographs of the southern heavens. 



.Artificial Imitation of Lunab L.andscape. — By cooling 

 the slag from an iron-ore, smelted in a furnace and run 

 off at a temperature of about 1100° C, Mr. Paul Fuchs 

 succeeded in obtaining a surface structure which appears 

 to be a very good imitation, in miniature, of a typical 

 lunar landscape. The cooling was done with water applied 

 in various ways, and produced craters, mountains, and 

 plains according to the conditions of the slag and of the 

 cooling. Photographs of the results are reproduced on a 

 plate accompanying No. 434R of the Astroiwmische Xach- 

 richtcn, wherein Mr. Fuchs describes his experiments. 



Temperature and Pressure Conditions in the Solar 

 Atmosphere.— Two interesting letters dealing with the 

 conditions obtaining in the solar atmospheres appear in 

 No. 413 of the Observatory (September, pp. 359-63). 



In the first, .Mr. Buss returns to the question of the 

 radial motions in sun-spots exhibited by Mr. Evershed's 

 spectrograms, and shows how they may' be interpreted to 

 indicate that the visible umbral area of a spot is caused 

 by the eftlux of material from within rather than the influx 

 of cooler matter from above. The facts that spots often 

 endure for months, and that .Mr. Evershed finds that the 

 radial motions are confined to the "reversing layer," i.e. 

 to the lower levels of the sun's general atmosphere, are 

 quoted as supporting this view; the vortices are effects of 

 the outrush. This idea of the spots being produced by 

 effluence leads to the sequel that the vapours of the actual 

 spot must be at a higher temperature, w-hereas the observa- 

 tions of Sir Norman Lockyer and others show the reverse. 

 To overcome this difficulty Mr. Buss suggests that the 

 spectrum observed is that of the vapours high above the 

 visual umbral level, and that, could we but observe the 

 unveiled spectrum of the umbra itself, we would find it 

 to be a bright-line spectrum. 



In the second letter Mr. Evershed continues the dis- 

 cussion with Prof. Whittaker regarding pressure in the 



reversing layer." After quoting experimental evidence 

 to show that pressure-shifts are apparentlv independent of 

 the manner in which luminositv is produced, Mr. Evershed 

 points _ to the fact that the spectrum of the "reversing 

 layer consists of bright lines, as demonstrating that there 

 is_ no enormous pressure on the emitting vapours ; other- 

 wise one would expect a more continuous spectrum. 

 Hnally, he states that measures of spot spectra, made at 

 IsodaikAnal, do exhibit small, differential pressure-shifts- 

 the most affected lines are slightlv displaced, rel.ativelv,' 

 towards the violet, thus indicating a pressure in the 

 umbra? of about one-third of an atmosphere less than in 

 the surrounding regions. Further details of these results 

 are to be published shortly. 



Parallax of the Double Star 2 2398.— In No. 4348 of 



the Astronomische Nachrichleti (p. 6-,), Dr. Karl Bohlin 



announces that the reduction of photographic observations, 



made at the Stockholm Observatory during 1907-8, shows 



NO, 2081, VOL. 81] 



that the parallax of the double star 2 2398 is 0484". This 

 star thus becomes the nearest known neighbour, in the 

 northern sky, to the solar system, its distance being 426,000 

 astronomical units, or 67 light-years. A previous observa- 

 tion by Lamp, at Kiel in 1883-7, gave the parallax as 

 0-353"- 



OUR FOOD FROM THE WATERS.^ 



A T the last meeting of the British .Association in Canada 

 ■^ (Toronto, 1S97) I was able to lay before Section U 

 a preliminary account ,of the results of running sea-water 

 through four silk tow-nets of different degrees of fineness 

 continuously day and night during the voyage from Liver- 

 pool to Oucbec. During the eight days' traverse of the 

 North ."Atlantic, the nets were emptied and the contents 

 examined morning and evening, so that each such gather- 

 ing was approximately a twelve-hours' catch, and each 

 day and each night of the voyage was represented by fom- 

 gatherings. This method of collecting samples of the 

 surface fauna of the sea in any required quantity per day 

 or hour from an ocean liner going at full speed was 

 suggested to me by Sir John Murray of the Challenger 

 Expedition, and was first practised, 1 believe, by Murray 

 himself in crossing the Atlantic. I have since been able 

 to make similar traverses of several of the great oceans, 

 in addition to the North Atlantic, namely, twice across 

 tlie equator and through the South Atlantic, between 

 England and South Africa, and four times through the 

 Mediterranean, the Red Sea, and the Indian Ocean to 

 Ceylon ; and no doubt other naturalists have done much 

 the same. The method is simple, effective, and in- 

 expensive ; and the gatherings, if taken continuously, give 

 a series of samples amounting to a section through the 

 surface layer of the sea, a certain volume of water being 

 pumped in continuously through the bottom of the ship,' 

 and strained through the fine silk nets, the mesh of which 

 may be one two-hundredth of an inch across, before pass- 

 ing out into the sea again. In examining with a micro- 

 scope such a series of gatherings across an ocean, two 

 facts are brought prominently before the mind : (i) the 

 constant presence of a certain amount of minute living 

 things ; (2) the very great variation in the quantity and in 

 the nature of these organisms. 



Such gatherings taken continuously from an ocean liner 

 give, however, information only in regard to the surface 

 fauna and flora of the sea, including many organisms of 

 fundamental importance to man as the immediate or the 

 ultimate food of fishes and whales and other useful 

 animals. 



It was therefore a great advance in planktology when 

 Prof. Victor Hensen (1887) introduced his vertical, quanti^ 

 tative nets, which could be lowered down and drawn up 

 through any required zones of the water. The highly 

 original ideas and the ingenious methods of Hensen and 

 his colleagues of the Kiel School of Planktology — whether 

 all the conclusions which have been drawn from their 

 results be accepted or not — have at the least inaugurated 

 a new epoch in such oceanographic work, and have in- 

 spired a' large number of disciples, critics, and workers 

 in most civilised countries, with the result that the dis- 

 tribution of minute organisms in the oceans and the fresh 

 waters of the globe is now much more fullv known than 

 was the case twenty, or even ten, years ago. But perhaps 

 the dominant feeling on the part of those engaged in this 

 work is that, nol\viih-;tanding all this activity in research 

 and the mass of published literature which it has given 

 rise to, much still remains to be done, and that the 

 planktologist is still face to face with some of the most 

 important unsolved problems of biology. 



It is only possible in an address such as this to select 

 a few points for dmionstration and for criticism — the 

 latter not with any intention of disparaging the stimu- 

 lating work that has been done, hut rather with the view 

 of emphasising the difficulties, of deprecating premature 

 conclusions, and of advocating more minute and more 

 constant observations. 



The fundamental ideas of Hensen were that the 

 plankton, or assemblage of more or less minute drifting 



^ Evening Hiscourse HeliverfH before the British .Association at Winnipeg 

 on August 31 by Prof. W. A. Herdman, F.R.S. 



