576 



NA TURE 



[April 19, 1894 



Adams prize essay on "The Mean Density of the Earth," in 

 which I have to-day read the following paragraph : — 



"The author is to be congratulated on the strictly scientific 

 title under which he describes his work — 'The Determination 

 of the Mean Density of the Earth,' or 'The Determination 

 of tlie Constant of Gravitation,' instead of the utterly unmean- 

 ing 'Determination of the IVeight of the Earth,' which is 

 found even in such a work as Arago's Populai- Asti-oiioiny, and 

 which is a characteristic of too much of our modern popular 

 science n la mode. Have we not seen in some old and popular 

 treatise a picture of ' the room in which Mr. Baily weighed the 

 earth ' ? It is to be hoped that some day our leading autho- 

 rities will be induced to abandon that fatal dogma which is still, 

 unfortunately, ' of great emolument ' — that science, to be 

 popular must, above all things, be inaccurate." 



As comment, I remark that the earth's weight, or mass, is 

 6*i4xio-i tons. What is unmeaning or unscientific in this 

 clear, intelligible, and accurate statement? 



Prof. Poyniing's work was in fact, directly and simply, a 

 weighing of the earth against a lead weight on the same 

 principles, and by the same instrument, as a grocer weighs a 

 quantity of tea against brass or iron weights, with inference 

 calculated by aid of the additional knowledge of the earth's 

 radius, " The determination of the constant of gravitation ''" 

 is a deduction requiring, not a knowledge of the earth's radius, 

 but the knowledge (derived from pendulum experiments) of 

 the gain of velocity, per unit of time, which a free falling body 

 would experience at the place of the gravitational weighings. 

 The critic is of course quite right in applauding Prof. Poynting's 

 double title, but he is not right in decrying the simple, clear, 

 and scientific expressions, "weighing the earth" and "the 

 weight of the earth." 



In Cavendish's original experiment, and in Baily's repetition 

 of it, and in Cornu's corresponding experiment with mercury 

 instead of lead, the more immediate result is "the constant of 

 gravitation " : the weight of the earth and the earth's mean 

 density are deductions. 



The "constant of gravitation " is not a very good or logical 

 expression, though it is not quite so bad as "coefficient of 

 friction," or "coefficient of thermal conduction," or "co- 

 efficient of self-induction." 



"Constant of gravitation" does not explain itself, either to 

 the learned scientific mind, or to the intelligent, non-scientific, 

 reader. K. 



April 10. 



The Royal Society. 



It may interest your readers to see the kind of foundation on 

 which rumours with regard to the Royal Society are based. 

 The following paragraph is from the Daily Chronicle of April 

 16, and the fact is that neither the Council nor the officers have 

 as yet met to consider the claims of the numerous candidates. 



John Evans. 



The Royal Society, Burlington House. 



"It is reported that the list of successful candidates for 

 admission into the Royal Society, which will be issued in a few 

 days, is not calculated to allay the acrid criticism to which the 

 council has of late been subjected. Far apart from its contain- 

 ing some very obscure names, and rejecting some much more 

 notable ones, the official selection, if all tales are true, will 

 exhibit more than ever the influence of that "professorial " 

 element into whose hands the Society has been getting more and 

 more every year. The election of Sir Henry Ho worth, which 

 few approved of, was really due to his rejection being advocated 

 by that unpopular clique, the members at large protesting in 

 their rather futile fashion against the nepotism of University and 

 South Kensington officials. This year, however, the college 

 tutor and the tripos hero is said to be more and more in favour. 

 By the way, it is curious to find that Mr. Selous, who has con- 

 tributed so many papers to the Royal Geographical Society and 

 was one of its gold medallists, has only now cared to be elected 

 a Fellow. Bat neiiher Nansen nor Hector, who shared in the 

 same distinction, are enrolled in the Society's membership. One 

 would imagine that a medallist ought to be an honorary Fellow, 

 more especially as some very peculiar people appear dans cette 

 Paler e" 



Lepidosiren paradoxa. 



The villi of the pelvic fins of this fish, referred to by Prof 

 Lankester in the last issue of Nature, have been already 

 briefly described by Prof Ehlers {Nachr. Kais. Gesellsch. do- 

 IViss. Gottingen, 1894, No. 2), as was shown by Dr. Giinther in 

 commenting upon them before the Zoological Society on the 3rd 

 inst. Dr. Giinther advanced good reason for regarding the villi 

 as sexual and confined to the male, as is implied in Prof Lan- 

 kester's letter. A specimen of a fine male has recently come into 

 my hands, in which, in contradistinction to all others yet described 

 in print, the " anus " (cloacal aperture) is located to the right of 

 the median ventral fin ; and it is thus proved that Lepidosiren, 

 like Protoptertis, is individually variable in the inter-relationship 

 of these two parts of its body. Being aware that Brock had 

 recently described the histological structure of dendritic processes 

 occurring in the neighbourhood of the genital orifice, in the male 

 ol Ploiosiis {Copidoglanis) anguillaris and in the two sexes of 

 Gasterotokeusbiaculeahis, I requested my pupil Mr. J. Sumner to 

 make sections of those oi Lepidosiren, hoping that erectile tissue 

 and tactile organs, such as Brock describes, might have been 

 present. We can find neither. The villi are highly vascular 

 and non-muscular. Dr. Bohls, who captured the specimens that 

 have lately reached Europe, has signified his intention of work- 

 ing out these structures in full ; and it is fair to him to assume 

 that he is in possession of material specially prepared for the 

 purpose. 



My specimen is further remarkable for an inequality in growth 

 of the pelvic fins — that of the (right) side on which the cloacal 

 aperture occurs exceeding its fellow in length by a quarter of an 

 inch; and, in view of Prof. Lankester's assertion that the forward 

 position of the pelvic fin is one "which the animal can give it 

 in life," the fact that the right pectoral is in my specimen 

 forwardly thrust into the branchial chamber may not be without 

 interest. 



No one can doubt the generic distinction of Lepidosiren 

 and Protopteriis ; indeed, the late Dr. Anton Schneider fully 

 established this, in reply to Ayers' proposal to regard them as 

 mere varieties of a common species. And it may he incidentally 

 remarked that prior to the acquisition of Dr. Bohl's specimens, 

 authoritative records of six museum preserved examples were 

 established {cf. Nature, vol. xxxviii. p. 126). 



G. B. Howes. 

 Royal College of Science, April 16. 



The Aurora of March 30. 



On the night of March 30 there occurred here an exception- 

 ally brilliant auroral display, remarkable, in this latitude, in 

 several respects. When I saw it I was a few miles north of the 

 city proper, and the southern horizon was lit up by the lights in 

 town, so that any faint display near the horizon to the south 

 would have been obscured. I first noticed the aurora about 

 8.30 p.m. (75th meridian east of Greenwich time), and it con- 

 tinued till midnight, but was much fainter and confined to a 

 simple glow in the north-west to north-east after about ten 

 o'clock. When first noticed, the sky from east to west round by 

 north was either quite deep red or reddish white. No clouds 

 were then visible, and there were no streamers, though the glow 

 extended about to the zenith. Then, as the red grew fainter, 

 a few small clouds formed in the north, and the still glow was 

 confined to the sky from east to west along the horizon, and 

 about 50° above it in the north, but less in the east and west. 

 From this arch of light, streamers shot up, not only from the 

 north but from east and west (or east by south and west by 

 south), and met in a place about id" south of the zenith. These 

 streamers pulsated rapidly, the light at times starting at the arch 

 of (apparently) still glow and travelling without break to the 

 point of meeting. At other times the glow would appear in 

 places along the course of the former streamers — first near the 

 arch, then further on, disappearing again, to again appear nearer 

 the zenith. When these rays met in the place south of the 

 zenith, their paths sometimes crossed, but more generally the 

 rays seemed to mingle and either form a roundish glowing spot 

 about 5° to 10° across, or a roundish, confused mass of glow 

 that looked like glowing smoke. Occasionally an appearance 

 like a hollow-centred whirlpool appeared. When the rays met 



NO. 1277, VOL. 49] 



