582 



NATURE 



{April 2 1 , I ! 



on "Continuous Calculating Machines," in the Philosophical 

 Transactions of the Royal Society, part ii., 1885. 



This note, whilst giving due priority to M. Ventosa in the 

 matter of one of the two features of the sphere and roller 

 integrator, described in the above paper, a feature at which I 

 need scarcely say I arrived quite independently, points to the 

 fact thai this forms but a part of the integrator in question. 

 When combined with the other portion, that integrator is a cal- 

 culating machine in the widest sense of the term. I have shown 

 that in addition to giving the value of 



fyJx, 



where y is any linear function of x, other varieties of the 

 mechanism obtain the value of such expressions as 



h,{x)F„(x) . . . F„{xyx, 



fh 



X, y)dydx, 



and also by a converse process give appro-ximately the value at 

 any instant of R where 



A. - dy 



I had not before to day seen the paper of Mr. F. J. Smith in 

 the Phil. JSIag. (August 1886), referred to by M. Ventosa. On 

 pp. 3S1 and 3S2 of my paper above alluded to will be found a 

 description of an integrator which is practically identical with 

 that of Mr. .Saiith, as I have no doubt he will admit when he 

 reads that description. With that integrator JioUow brass balls 

 were employed for the very purpose suggested by Mr. 

 Smith. The instrument was, however, abandoned in favour of 

 more convenient forms, one of which was actually employed by 

 that gentleman upon his " ergometcr " at the Inventions Exhi- 

 bition, together with some very ingenious integrators of his own 

 design. There is, I would say, one point of difference between 

 the integrator described by Mr. Smith, and that by myself. 

 The movable arm in the former a]ipears to be guided liy a pin 

 in a straight slot. Now in the "sine" form, of which this 

 inte,.;rator is an example, this pin should move in the arc of a 

 circle, and it would be interesting to know if approximately 

 correct results have been obtained with what is in some respects 

 a more convenient practical device. 



H. S. Hele Shaw 

 University College, Liverpool, April 9 



The Vitality of Mummy Seeds 

 I READ with much surprise in Natuke of March 31 (in Prof. 

 Judd's defence of his statement as to the longevity of seeds) 

 that "competent botanists have cited the case of the germination 

 of seeds taken from ancient Egyptian tombs as authentic." 

 Many experiments have been made as to the length of time seeds 

 may retain their power of germinating, by Robert Brown, 

 Henslow, and others, with interesting results as to the long- 

 evity of some ; but my impression is, and I venture to make 

 it public, that competent botanists have universally condemned 

 as utterly worthless the evidence given in support of alleged 

 instances of the germination of mummy seeds. No scientifically 

 responsible person has, so far as I am aware, put the fact on 

 record. In these circumstances, therefore, the results of the 

 successful experiments refened to farther on by Prof. Judd as 

 haying recently been made, possess the greatest interest, and 

 botanists will look forward eagerly to the details which it is to 

 be hoped will soon be made public. Hitherto the fruitful source 

 of error has been the deception at the outset of the credulous 

 experimenter by the Arab. In fact, the mummy wlicat of one 

 well-known traveller grew up in the form of ca/j- -a plant not 

 cultivated by the ancient Egyptians, but now grown in the land 

 they inhabited — though this did not shake his faith in the 

 genuine source of his supply. In the present case, however, the 

 statement made in faith by so high an authority as Prof. Judd 

 leads us to anticipate that the undertakinj has been hedged in 

 with all the safeguards demanded by a pure cultivation of 

 undoubtedly genuine material. George Murray 



7 Onslow Place, South Kensington, S.W., April 5 



Solar Halos 



In the forenoon of March 6 the sun was surrounded by a 

 series of halos of the form shown in the diagram. The side of 

 each arc, marked with a wavy or saw-toothed outline, was red, 

 and the opposite edge blue ; but no colour at all was visible in 

 the horizontal belt nor in the farthest-out halo (H3). This 

 sketch shows the ap]3earance at about 9 a.m. ; as the sun rose 

 higher, the horizontal belt got a curve upwards at each side — 

 i.e. it continued to be parallel to the horizon — aud was prolonged 

 inside Hj till it almost touched the sun. The two mock-suns 



were distinctly on the outside of Hj, and were coloured red 

 next the sun, and blue outside, their reds about coinciding 

 with the blue of Hj. The following are some of the measure- 

 ments : — 



Sun to western mock-sun 

 ,, eastern ,, 



H3 (two measurements). 



... 23 46 



... 23 42 



i79 56 



•••|8i 23 



The halo Hj has, I believe, been very seldom seen, and there 

 are only three estimates of its radius on record : two of these 

 make it 90°, and the third makes it 85° to 90°. It will be seen 

 that our measurements — both about 81° — are considerably less 

 than any of the former ones. R. T. Omond 



Ben Nevis Observatory 



On the Character of the Beds of Chert in the 

 Carboniferous Limestone of Yorkshire 



It may be of interest to geologists to kno.v that I have lately 

 ascertained that the beds of chert which occur in the limestones 

 of the Ycredale series of Yorkshire are distinctly of organic 

 origin, and that, in fact, they are composed of the heterogene- 

 ously-mingled spicules of disintegrated siliceous sponges The 

 beds vary from 3 inches to iS feet in thickness, and the lime- 

 stones in which they are interbedded are nearly exclusively com- 

 posed of the broken-up remains of crinoids, thus showing a 

 well-marked alternation of periods in which sponges and 

 crinoids succeeded each other. The spicules can only be .studied 

 in thin microscopic sections of the rock ; in some cases they are 

 very perfectly preserved and their axial canals are clearly shown ; 

 in other examples only very faint outlines can be made out. 

 They appear to belong for the most part to the same group of 

 Hexactinellid sponges as the recent genus Hyjlonema, but 

 Monactinellid spicules, like those of the existing genus Renicra, 

 are also very nu uerous in some of the beds. Such an enormous 

 accumulation of the debris of siliceous sponges proves that these 

 organisms were as abundant in the Carboniferous as in the 

 Cretaceous seas 



The beds of chert referred to are exposed near Harrogate, and 

 at Richmond, Yorkshire, and they are remarkably developed 

 at Arkendale, about fourteen miles above Richmond. I am 

 indebted t ) Mr. J. G. Goodchild, of the Geological Survey, for 

 directing my attention to this last-named locality. Owing to 

 their resistant character, fragments of the beds are also widely 

 distributed in the boulder-clays to the south of their outcrops, 

 and I have met with them in these clays near York. 



It has been known for some time that the remains of siliceous 

 sponges are of comnon occurrence in the Carboniferous chert 

 beds of Ayrshire and of certain parts of IreUnd, but they do not 

 appear to have been noticed hitherto in the corresponding beds 

 of Yorkshire. I hope shortly to give a more detailed descrip- 

 tion of their principal characters. George J. Hinde 



Croydon, April 2 



