April 22, 1875] 



NATURE 



play irregularly, and the Law of Fatigue will not apply to them ; 

 and the statement of that law leading to the cubical hyperbola 

 must be modified as follows : — 



Let there be m fibres tired out, 



And 11 fihres worked but not tired out ; 



And let .V be the mean weight held in the hand lifted by 

 the fibres « ; then the weiglit really lifted by the fibres m will be 

 (w+ o - x). And it is to t!iis quantity only that the Law of 

 Fatigue applies, giving us the formula 



n (it/ + a - x) " = A. (4) 



In Mr. Nipher's first set of experiments at fixed rale we 

 found — 



a - X = + I -094. 

 And in his experiments now published we have — 

 a - .r = - I -276. 



From this (supposing the experiments not damaged in their 

 reduction) I should infer that the supraspinatus and acromial 

 deltoid were aided, irregularly, in the two cases by muscular 

 fibres (not tired out), which lifted respectively o'4i and 277 

 kilos. 



Trinity College, Dublin, Samuel Haughton 



March 13 



P.S. — I have received a letter from Prof. Gustavus Hinrichs, 

 of Iowa State University, in whose laboratory Mr. Nipher was 

 assistant, and who gave Mr. Nipherall possible aid in his expe- 

 riments. In this letter Prof. Hinrichs states that Mr. Nipher's 

 former experiments were in fact as good as those he last made. I 

 myself believe that, in some respects, they were better. 



Denudation 



Many students of geology find a difficulty in realising that the 

 effects of denudation are due to the simple action of w.iter set in 

 motion only in ways familiar tu us. To ihem, and indeed to many 

 others, it may be of some interest to observe a working model 

 which, though made without any such design, shows with curious 

 fidelity, on a small scale, the effects which have been produced in 

 the lapse of ages on the great features of cur globe. 



Londoners will remember that the Serpentine was emptied, 

 cleaned out, and finally refilled about five years ago. Coping- 

 stones of hewn granite were laid along the mnrgin of the foot- 

 path, and from this, slanting down for about two feet, was a 

 layer of concrete laid about the level of the water line. Possibly 

 this concrete was not of the most durable quality, still it was 

 certainly harder than most of the rocks which bound our coasts. 

 But in the short space of about five years the tiny wavelets of 

 this littlle lake have worked this smooth slof'ing hill into a bold 

 and rugged line. In some places, indeed, all the corcrete has 

 been washed away, and there is a sandy beach right up to the 

 granite. Two or three years ago the water was at a somewhat 

 lower level than it is now. The traces of the change are 

 recorded, especially on the north side, a little to the east of the 

 boat-houses. There, a double range of " cliffs," one over the 

 other, is to be seen extendmg for some considerable distance. 



This " niodi-r' is indeed of so much interest that I ask you to 

 insert this notice of it, for I am sure that many of the readers of 

 Kature would share the pleasure I have felt in watching the 

 very striking similarity in effects produced by the same agents 

 wbrking on scales so vastly different. R. H. 



OUR ASTRONOMICAL COLUMN 

 The Sun's P.\rallax. — In Astron. Nach., No. 2^033, 

 Prof. Galle, Director of the Observatory of Breslau, gives 

 his final deductions with reference to the value of solar 

 parallax from corresponding observations of the minor 

 planet Flora, about the opposition of 1873, which took 

 place while the planet was near perihelion. Observations 

 with this special object in view were made at the Observa- 

 tories of Bothkanip (Herr von Bulow), Cape of Good 

 Hope, Clinton (N.Y.), Cordoba, Dublin, Leipsic, Lund, 

 Melbourne, Moscow, Parsonstown (the Earl of Rosse), 

 Washington, and Upsala ; by 37 N. and 36 S. stars, the 

 sun's parallax is inferred to be 8"-879 (± o '"0396), which, 

 singularly enough, is the exact figure lately communicated 

 by M. d'Abbadie to the Astronomer Royal, as a first 

 result obtained by M. Puiseux, from observations of the 



recent Transit of Venus at the French stations at Pekin 

 and St. Paul Island. 



TuTTLE's Varuele Neeula IN Draco, &c.— This 

 object well deserves regular observation, the evidence in 

 favour of its variability being apparently beyond question. 

 It was first seen by Tuttle in September 1859, and occurs 

 in Argelander's Durchmusterung. On the 24th of Sep- 

 tember, 1 862, D'Arrest, observing with the Copenhagen 

 refractor, describes it as a large bright nebula, 2' long 

 and So" broad, and he adds : " bene conspicienda tubo 

 quasstore." On the 22nd of August, 1863, after re-exami- 

 nation, he has the note : " I think this nebula was far 

 brighter in the year 1862," and on the 12th of the follow- 

 ing month he remarks ; " tubo quasstore non amplius 

 discernilur." In a letter to Sir John Herschel, he ex- 

 presses his conviction that the nebula could not have 

 been so bright as it was in September 1862, in the tirnt 

 of Sir W. Herschel and Messier. Auwers, in K6nii;s- 

 berg Observations, xxxiv. p. 227, says he found the nebula 

 pretty bright, 2i' long, li' broad, the direction of the 

 longer diameter being 50°. If we take the mean of 

 D'Arrest's observations for position {Sideruni Nebulo- 

 j(?;7/OT, &c,p. 333), and bring up to the commencement 

 of 1875, 'he following place results : — 



R.A. ... i8h. 23m. i6s. N.P.D. ... 15° 29'-5 



This nebula is No. 4,415 of Sir John Herschel's general 

 Catalogue. We are able to state that there is some 

 suspicion of variability about No. 4,369 of the same Cata- 

 logue (Hind, 1852, April 26), and possibly in the small 

 hazy-looking star preceding the brightest part of the 

 nebula. In April 1852 it was very small and rather faint, 

 perhaps I'in diameter; it followed Lalande, 33076, 50-15., 

 and was 9'-4 north of the star. Auwers (Konigsberg 

 Observations, xxxiv. p. 227) found it pretty faint, 2' 

 diameter, gradually a little brighter towards the middle ; 

 a star 12th magnitude situate on the border of the nebula 

 on an angle of about 230" from its centre. Later obser- 

 vations have afforded indication of fluctuating brightness, 

 but are not decisive. Auwers thought he found signs of 

 variability in the nebula No. 4,473 (Hind, 1845, March 30). 

 In a 6-feet Fraunhofer it was pretty bright, round, and from 

 two to three minutes in diameter ; and once, i860, Aug. 16, 

 with the Konigsberg heliometer it was " surprisingly faint 

 and of the second class at the highest." Schonfeld has seve- 

 ral obsei-vations vaAstionomiiclieBcob. zii Maiiheiin, 1862 ; 

 the diameter is variously recorded between 45" and 2', 

 and once it is remarked that the nebula showed strong 

 scintillation and appeared resolvable. D'Arrest, who 

 independently discovered this nebula in the spring of 

 1S52 {Asiron. Nach., No. 809) has given his earlier obser- 

 vations in Rcsultate aiis Bcob. dcy Ncbeljleckcn, Erste 

 Rcihe; in September 1855 he suspected it might prove a 

 cluster of very minute stars. His later observations with 

 the Copenhagen refractor are published in Sidciiim 

 Nebulosorini!, &c., where he states that he had not, 

 during sixteen years, noticed any change either of bright- 

 ness or position ; and he mentions further that in April 

 1866 he detected a number of luminous points. Varia- 

 bility in the case of this object appears hardly to rest 

 upon sufficient proof, considering the effect of indifferent 

 nights upon such observations, but it is suggested in Sir 

 John Herschel's last Catalogue, and on that account is 

 referred to here. 



Comet 1766 (II.) — If Burckhardt's elliptical elements 

 of the second comet of 1766, discovered at Paris on 

 April 8, are approximately correct, it is not improbable 

 that the comet was observed on its first perihelion pas- 

 sage with that form of orbit. Burckhardt succeeded in 

 representing the rough observations of La Nux at the 

 Isle of Bourbon, extending to May 13, by an ellipse with 

 a period of only five years, Pingrd having failed in bring- 

 ing them into satisfactory agreement with the few obser, 

 vations taken by Messier and Cassini de Thur)', at Paris- 



