Oct. ^o, 1879] 



NATURE 



625 



stated in the introduction to the volume, the influence of omitted 

 days was duly taken into account, values for such days being 

 adopted from the eye-observations (usually six daily) corrected 

 for diurnal inequality by means of corrections derived from the 

 discussion of the twenty years' photographs. Thus, among the 

 twenty separate daily values on which each mean daily value in 

 Table 77 depends, one or two may be derived from eye-observa- 

 tions in the way described. 



The diurnal variation of temperature in the apartment in 

 which the photographic barometer is placed is, on the average, 

 less than one degree. William Ellis 



Royal Observatory, Greenwich, October 27 



Sun-Spots in Earnest 



With reference to the fine group of sun-spots to which Prof. 

 Piazzi Smyth draws attention in Nature, vol. xx. p. 602, it 

 may be interesting to mention that the incipient stage of the 

 group in question is shown on two photographs of the sun taken 

 at the Royal Observatory, Greenwich, on October 16 (two days 

 before the date of Prof. Piazzi Smyth's observation). At that 

 time the group consisted of three "veiled" spots and several 

 very small specks hardly to be distinguished from the ordinary 

 pores, together with small faculae. No photographs were ob- 

 tained on the next day, and on October 18 enormous changes 

 had taken place, the "veiled" spots having developed into fine 

 sunspols, with nucleus and penumbra. Four photographs taken 

 on this day show that changes were still taking place, and these 

 contmued throughout the remainder of the period of visibility of 

 the group, viz., till October 21, when it passed offat the west limb. 

 No trace of the group is to be found on two photographs taken 

 on October 15, so that it would appear to have formed behveen 

 October 15 and 16, and must have been quite in its infancy 

 when first photographed on October 16, being then very nearly 

 on the central meridian. 



Several small spots have appeared on the sun lately, but they 

 have been for the most part very short lived. Thus a group of 

 spots with facula;, first seen on the east side of the sun on October 

 IS, had completely disappeared on October 16. Another group 

 consisting of six or seven small spots with faculce, which appeared 

 at the east limb on October 7, had completely closed up in the 

 interval between October 10 and 15. On the whole the Green- 

 wich photographs seem to support Prof. Piazzi Smyth's conclu- 

 sion that the period of quiescence is now over, and that the solar 

 activity is decidedly on the increase. W. IT. M. Christie 



Royal Observatory, Greenwich, October 25 



The Kew solar observations now are, unfortunately, limited 

 to a daily inspection of the sun through a 3-inch telescope, and 

 the drawing of a rough sketch of the spots on its surface, should 

 any be visible, the object the Committee have in view being merely 

 a continuation of the enumeration of the groups as they make 

 their appearance, in the same manner as did Ilofrath Schwabc. 



I have referred to the sketches drawn on the 15th, i6th, 17th, 

 and l8th instants, in order to see what records they afford of the 

 outbreak of the group of spots mentioned by Prof. Piazzi Smyth 

 in Nature, vol. xx. p. 602, and find we noted on the 15th two 

 small spots in the sun's northern hemisphere. These were not 

 seen on the l6th, the disk being entered in the register as having 

 "no spots," but at 10.30 a.m. on the 17th a group of small 

 spots appeared to the south of the equator, just in the place 

 occupied on the next day by the group of gigantic spots to which 

 attention has been directed, allowance of course being made for 

 the sun's rotation. 



These observations show that the spots did not suddenly burst 

 forth in their full grandeur, but that they broke through the sun's 

 urface gradually, that is to say, the explosion, if such it was, 

 extended over more than twenty-four hours. 



In the cxamiilation of the Kew solar photograms from 1863 

 to 1872 now in progress here under the direction of Mr. De la 

 Rue, we have fonnd several instances of similar extensive changes 

 in spots from day to day, not only in the eruption of large spots, 

 but also in their closing up in an equally short space of time. 



To give more recent instances, I find that a considerable group 

 of spots was observed on June 28, of which we had no record on 

 the 25th ; and again, on July 11, some large spots were noted, 

 whilst on the preceding day, July 10, "no spots" was entered 

 in the register. 



The magnetograph curves show a slight disturbance of the 



magnetic elements on the l6th and 17th, but during the 18th the 

 needle simply recorded its ordinary daily range. 



I trust that better-equipped observers will be able to give you 

 more exact accounts of this interesting phenomenon. The sun- 

 shine recorder here indicated continuous sunshine on the i6th, 

 occasional gleams on the 17th, and seven hours on the i8th, so 

 the climate cannot be blamed for any shortcomings on the part 

 of southern observers on this occasion. G. M. AVhiitle 



Kew Observatory, October 25 



The conclusion as to the increasing activity of the solar sur- 

 face, drawn by the Astronomer-Royal of ScoUand fi-om his 

 observations of a large solar spot on the iSth instant, is strongly 

 confirmed by the present state of the south-east quarters of the 

 sun s disk. Few prominences are now visible in the other por- 

 tions of the limb, but on the 26th at 23" 10' E. of the south point 

 (direct image), the bright line C of the chromosphere extended 

 to the height of 3' 43" from the limb, and this morning-, the 28tb, 

 the greatest height was i' 17" at 18° 46' E. of S. On the 28th 

 the remarkable prominences extended along the limb from— 



iS'S'E. ofS. to38'E. of S., 

 and this'morning they were traced from — 



la' 51' E. of S. to 20° 2i'. 

 The ordinary level of the chromosphere does not extend above 

 5 ' from the limb, but to-day it was rather over 6". 



Eight prisms of 60° were used in a Browning automatic spec- 

 troscope adapted to an S-inch achromatic. S. J. Perry 



Stonyhurst Observatory, October 28 



Wallace's "Australasia" 



Allow me to thank the writer of the review in Nature, 

 vol. XX. p. 597, for some valuable criticisms of my book. It is 

 quite refreshing after the common-place praises of most reviews 

 to have one's errors pointed out and omissions noticed, and I 

 hope to make use of such corrections in a forthcoming new 

 edition. At the same time there are a few points on which I 

 wish to say a word. In the first place the book is not a scientific 

 work, but one of a series intended, as expressly stated, "for 

 general reading." This Ls, of course, no excuse for errors, but 

 it is a sufficient reason for giving general rather than detailed 

 descriptions of weapons, canoes, &c., and for occasionally stating 

 roughly the size of an article even when it varies greatly, in order 

 to give definite ideas to readers who may be complete strangers 

 to the w hole subject. 



I quite agree with my reviewer, that too much is included to 

 be properly treated in one volume, but that was a matter 

 dependent on the arrangement of the scries, over which I had no 

 control ; and as I had in the earlier portion of the work overrun 

 the space allotted me, I was obliged to restrict my notices of many 

 parts of Polynesia, which is no doubt the most imperfect portion 

 of the volume. It is here that the original work is most utilised, 

 and it will be found that most of the passages criticised (in- 

 cluding that in which I am charged with "becoming quite 

 poetical ") are Hellwald's. Of course, I should have corrected all 

 his small inaccuracies, but it was almost impossible to do so 

 without rewriting hLs work altogether. No doubt a very 

 interesting volume could be written on Polynesia alone by the 

 aid of the German authorities referred to by the reviewer ; but 

 when I state that the time allowed me for the composition of the 

 entire work was six months, and that I actually completed it in 

 eight, it will be seen that I was compelled to limit myself in the 

 study of authorities as well as in the space I could devote to 

 particular islands. 



I think my reviewer forgets the character of the book as 

 essentially geographical, when he objects to my treating New 

 Zealand apart from Polynesia ; hence I cannot admit the sound- 

 ness of his criticism on the comparison of the characters of the 

 Fijians and Polynesians, a comparison which, if I remember 

 tightly, is that of an author who knew them both thoroughly — 

 the Rev. G. Turner. I must also demur to the implication that 

 land can never have extended where there is now a sea 2,000 

 fathoms deep. I suggest (p. 564) an extension of New Zealand 

 as far as the Kermadee Islands as having possibly occurred 

 " i>t some remote epoch," and I certainly fail to sec its impossi- 

 bility ; yet this is what is suggested by my reviewer's remark, 

 that nnfortunately there is a depth of 2,000 fathoms between 



