Dec. 14, 1871] 



NATURE 



123 



science teachers, who have already enough grievances to urge 

 against the Department on the score of its administration, than 

 to obtain any amelioration of their status. 



I do not think many science teachers will endorse more than 

 one other of Mr. Uhlgren's complaints ; so that it is of the 

 greatest importance that that one which affects them all should 

 be proved in the fullest and most circumstantial manner. 



Plymouth, Dec. 9 A Local Committee-Man 



Lunar Calendars 



I WISH to call attention to the variations observable between 

 the true period of new moon and the commencement of lunar 

 months, as set forth in the following table : — 



Period of New 

 Moons 



Jewish Cilenda 



A.M. 5632.3 



Mahomedan Calenda 



Jan. 10 2 58 P.M. Shebat commences 11 Jan. 12 Dulkaadah 



Feb. 9 1.52 A.M. ist Ajar ,, lo Feb. ii Dulhagee 



Mar. 9 0.53 P.M. 2nd „ „ ii Mar. 11 Mulharram 



April 8 0.32 A.M. Nisan „ 9 April 10 Saphar 



May 7 1.19 P.M. lyar „ 9 May 9 Rabia (i.) 



June 6 323 A.M. Sivan „ 7 June 8 „ (ii.) 



July 5 6.25 P.M. Tammuz „ 7 July 7 Gomada(i.) 



Aug. 4 9.46 A.M. Ab „ 5 Aug. 6 „ (ii.) 



Sep. 3 0.54 A.M. Ellul „ 4 Sept. 4 Rajah 



Oct. 2 3.31 P.M. Tisliri „ 3 Oct. 4 Shaban 



Nov. I 5.28 A.M. Heshvan ,, 2 Nov. 2 Ramad.4n 



„ 30 6.55 PM. Kislev ,, I Dec. 2 Shawal 



Dec. 30 6.36 A.M. Tebeth „ 31 „ 31 Dull;aadah 



As many eminent and practical astronomers write to Nature, 

 I shall be much obliged if some one will add a fourth column to 

 the above, fully explaining these ditferences. My object is to as- 

 certain if a calendar, founded on lunations, is at all susceptible 

 of tonversal use, so as to be correct to time in all places. The 

 true new moon is invisible, the visible new moon is not the true 

 new moon ; is there a medial average ? 



November 23 Myops 



Nev7 Zealand Forest Trees 



Let me recommend those of your readers who take an interest 

 in this subject, to trust for correct information thereanent to the 

 works whose names are appended, and not to the statements of 

 recent correpondents of Nature, who commit errors so great 

 as to refer Manuka to the genus or family ZJ/cywa .' 



(i) Dr. Hooker's " Handbook of the New Zealand Flora," 

 which contains at the end of vol. ii. an " Alphabetical 

 List of Native and Vernacular Names " of New Zealand 

 plants, including trees. 



(2) A similar Catalogue of Native and Vernacular Names, 

 publislred, subsequently to Dr. Hooker's list, by Dr. Hec- 

 tor, Director of the Geological Survey of New Zealand. 



(3) " Report and Award of the Jurors" of the New Zealand 



Exhibition of 1865 ; which contains at page 474 an admir- 

 able table — showing the strength and other qualities of 

 New Zealand woods, in connection with the names of the 

 trees yielding the said timbers — carefully drawn up by the 

 late Provincial Marine Engineer of Otago, J. M. Balfour, 

 C.E. ; and 



(4) The 3 vols, already published of the " Transactions and 



Proceedings of the New Zealand Institute." 



W. Lauder Lindsay 



Solar Halo 



.Seeing in your last number an account of a Solar Halo, it has 

 occuiTed to me that the following description of a similar phe- 

 nomenon, which I saw in Norway this autumn, may not be un- 

 interesting to some of your readers. 



The sun, at 4 o'clock p.m., was just setting behind a range of 

 mountains in the Romsdalen, when a bright halo of light ap- 

 peared round it, forming a clearly-defined circle, and at the crown 

 of tlie circle there appeared two horns, as of the beginning of 

 another circle inverted, the junction of the two circles being very 

 luminous ; the limbs of the inverted circle — if I may so call it — 

 were rather straight than curved, and were not very long. A 



second and outer circle, just twice the diameter of the inner one 

 shortly appeared, and this circle had all the colours.of a rainbow- 

 most distinctly visible. These two bows were strongly defined 

 for an hour at least, and during that time constant waves of lin-lit 

 sliot up and across the sky, not always from tlie centre, where 

 the sun was, but often from some point within the inner circle to 

 the south of its centre. At other times rays of light would shoot 

 out at a tangent from the outer bow, sometimes on one side and 

 sometimes on the other. Again, some would shoot from one 

 circle to the other, forming a .series of bars parallel Vkiih the 

 horizon, and at last the rays seemed to concentrate, and, radiating 

 from the centre of the inner circle, shot right through both circles 

 across the sky over our heads, forming a series of gigantic ribs 

 which extended from west to east. 



The day (it was September 23) had been perfect, with a bright 

 sun, a cold, frosty atmosphere, and a blue, cloudless sky. Snow 

 had fallen heavily about three days before, and was still lyino- 

 everywhere ; but on the day we saw this grand display not a 

 cloud had been visible from morning till evening. Afier all was 

 over, the clouds crept up, and we saw several brilliant shoots of 

 the Northern Lights. W, W. Harris 



Manningham, Bradford, Dec. 6 



Proof of Napier's Rules 



Such a structure m cardboard as that described by Prof. A. S. 

 Herschcl in Nature, No. io6, may be found veiy useful in 

 facilitating the study of the proof of "Napier's Rules," but the 

 ingenious learner might object that the demonstration was con- 

 fined to one particular species of triangle — the isosceles rii^ht- 

 angled with a perimeter equal to a quadrant ; for Mr. Herscltel's 

 angles a and b are plainly equal, and together with c make up a 

 right an ^le. The corresponding construction for any cjse would 

 be as follow : — Ta'ice a circular piece of cardboard with centre D 

 (referring to Mr. Herschel's diagram), and on the circumference 

 in the same direction, take any two arcs Bi, 12. Let a perpen- 

 dicular from B or Di meet it in D, and a second from C or D2 

 meet it in A, and be produced to reach the circumference in B'. 

 Finally, a semicircle on A B' as diameter and another with centre 

 A and radius A C will detennine by their intersection the point C. 

 To a construction thus generalised all that Prof. Herschel adds 

 would apply. 



As a question of " Queen's English," it seems hard to connect 

 the last clause in the first paragraph of Prof. Herschel's letter with 

 what precedes. "Them " can only refer grammatically to "diffi- 

 culties ; " but surely Mr. Cooley did not propose to himself ' to 

 render them as easily accessible as possible to the inquiring 

 student in mathematics." J. T. \^ 



The Cause of Specific Variation 



I have only just read Mr. Mivart's " Genesis of Species," and 

 was glad to find that his ideas, so ably expressed, are nearly, if 

 not quite, identical with my own, which I laid before the Vic- 

 toria Institute in a paper " On Certain Analogies between the 

 Method of Deity in Nature and Revelation,'"" iVIay 10, 1869. 

 On p. 259 of his " Genesis of Species " he has the following 

 remarks :— " But are there any grounds for thinking that, in the 

 Genesis of Species, an interna! force or tendency intervenes, co- 

 operating with and controlling the action of external conditions ?" 

 This question appears to me to exactly correspond with the sen- 

 timents of the following passage from the "Journal of the 

 Transactions of the Victoria Institute," vol. iv., p. 265.:— 



" Rather than venture on any attempt to explain the Divine 

 methods by ordinary terms, I would prefer adopting some general 

 expressions to convey an imagined idea of the causes of existing 

 things, and as less liable to the charge of anihropomorphism. 



" I purpose, therefore, adopting the general word force, and 

 rec-ignising all issues in nature as the effect produced upon maUer 

 by the resultant of component forces. These forces are separable 

 into physical, chemical, biological, &c. ; and, in addition to all 

 those which the chemist and the physicist can eliminate and claim 

 as the objects of their special studie-s, there still remains a residuum 

 of forces in those organisms endowed with lif--, and which produce 

 those results which we say are designed, and which it is customary 

 to regard as witnessing to a Divine Intelligence. 



"In recognising these latter forces, I would call them evolutive, 

 but as being so far like others that their resultant with them 

 produces relative effects only according as in their continual 



