April 26, 1888] 



NATURE 



609 



The passage from the second group to the third brings 

 us to those bodies which are increasing their tempera- 

 ture, in which radiation and fluting absorption have given 

 place to line absorption. 



At present the observations already accumulated have 

 not been discussed in such a way as to enable us to state 

 very definitely the exact retreat of the absorption, by 

 which I mean the exact order in which the absorption 

 lines fade out from the first members to the last in the 

 group. We know generally that the earlier species will 

 contain the line absorption of those substances of which 

 we get a paramount fluting absorption in the prior group. 

 We also know generally that the absorption of hydrogen 

 will increase while the other diminishes. 



The next group, the fourth, brings us to the stage of 

 highest temperature, to stars like a Lyrae ; and the 

 division between this group and the prior one must be 

 more or less arbitrary, and cannot at present be defined. 

 One thing, however, is quite clear, that no celestial body 

 without all the ultra-violet lines of hydrogen discovered 

 by Dr. Huggins can claim to belong to it. 



We have now arrived at the culminating point of 

 temperature, and now pass to the descending arm of the 

 curve of temperature. The fifth group, therefore, will 

 contain those bodies in which the hydrogen lines begin 

 to decrease in intensity, and other absorptions to take 

 place in consequence of reduction of temperature. 



One of the most interesting problems of the future will 

 be to watch what happens in bodies along the descending 

 scale, as compared with what happens to the bodies in 

 Group III. on the ascending one. But it seems fair to 

 assume that physical and chemical combinations will now 

 have an opportunity of taking place, thereby changing 

 the constituents of the atmosphere ; that with every de- 

 crease of temperature an increase in the absorption lines 

 may be expected, but it will be unlikely that the last 

 species in this group will resemble the first one in 

 Group III. 



The next group, the sixth, is Secchi's type IV. 

 and Vogel's Class \l\.b, its distinct characteristics 

 being the absorption flutings of carbon. The species 

 of which it will ultimately be composed are already 

 apparently shadowed forth in the map which accom- 

 panies Dundr's volume, and they will evidently be 

 subsequently differentiated by the gradual addition of 

 other absorptions to that of carbon, while at the same 

 time the absorption of carbon gets less and less distinct. 



To sum up, then, the classification I propose consists 

 of the following groups : — 



Group I. — Radiation lines and flutings predominant. Absorp- 

 tion beginning in the last species. 



Group II. — Mixed radiation and absorption predominant. 



Group III. — Line absorption predominant, with increasing 

 temperature. The various species will be 

 marked by increasing simplicity of spectrum. 



Group IV. — Simplest line absorption predominant. 



Group V. — Line absorption predominant, with decreasing 

 temperature. The various species will be 

 marked by decreasing complexity of spec- 

 trum. 



Group VI. — Carbon absorption predominant. 



Group VII. — Extinction of luminosity. 



It will be seen from the above grouping that there are 

 several fundamental departures from previous classifica- 

 tions, especially that of Vogel. 



The presence of the bright flutings of carbon associated 

 with dark metallic flutings in the second group, and the 

 presence of only absorbing carbon in the sixth, appears to 

 me a matter of fundamental importance, and to entirely 

 invalidate the view that both groups (the equivalents of 

 Ill.a and \\\.b of Vogel) are produced from the same 

 mass of matter on cooling. 



This point has already been dwelt upon by Pechiile. 



Another point of considerable variation is the separa- 

 tion of stars with small absorption into such widely 

 different groups as the first and fourth, whereas Vogel 

 classifies them together on the ground of the small 

 absorption in the visible part of the spectrum. But that 

 this classification is unsound is demonstrated by the fact 

 that in these stars, such as y Cassiopeiae and ^ Lyrae, 

 we have intense variability. We have bright hydrogen 

 lines instead of inordinately thick dark ones ; and on 

 other grounds, which I shall take a subsequent oppor- 

 tunity of enlarging upon, it is clear that the physical con- 

 ditions of these bodies must be as different as they pretty 

 well can be. 



It will be seen also that, with our present know- 

 ledge, it is very difficult to separate those stars the 

 grouping of which is determined by line absorption into 

 the Groups III. and V., for the reason that so far, seeing 

 that only one line of temperature, and that a descending 

 one, has been considered, no efforts have been made to 

 establish the necessary criteria. I made this point in the 

 paper to which I have already referred in connection 

 with the provisional curve, and for purposes of complete- 

 ness I introduce here the chief part of what I wrote on 

 that occasion. 



(71? be continued) 



THE HITTITES, WITH SPECIAL REFERENCE 

 TO VERY RECENT DISCOVERIES} 



C OME months ago the Rev. Greville J. Chester brought 

 •^ to this country a quadrangular haematite seal found 

 near Tarsus. Though this seal shows, in certain particu- 

 lars, some analogy with the Yuzgat seal, yet it gives little 

 or no additional aid in the decipherment of the inscrip- 

 tions. It presents, nevertheless, features of very great 

 interest. Prof Sayce scarcely goes beyond the merits of 

 the seal when he says that it possesses a " unique and 

 splendid character ; nothing like it has ever before been 

 brought to the notice of European scholars." ^ The seal 

 is engraved not only on the base (i), but also on the four 

 sides, while opposite the base the stone was so cut as to 

 serve the purpose of a handle. On four out of the five 

 engraved faces are to be seen two figures — one seated and 

 one standing. These may be supposed to represent men 

 or deities, or possibly, in some cases, ideal personages. 

 At first sight it may seem difficult to discern any general 

 aini or connected purpose in the curious figures depicted. 

 On more attentive examination, however, there is seen to 

 be exhibited a pervading principle of tri-utiity^ especially 

 as exemphfied in the triangle and the trident. Moreover, 

 while on three faces of the seal (i, 2, 5) there are figures 

 with the " pig-tail " (an appendage which suggests a con- 

 nection with the Hittites), it appears tolerably evident 

 that the engraver of the seal intended to represent the 

 personages with this appendage as destitute of the valu- 

 able knowledge and power connected with the mysterious 

 three-in-oneness of the triangle and the trident. This is 

 entirely in accordance with the position that the wearers 

 of the pig-tail were still regarded as aliens and intruders 

 when the seal was engraved. 



On the base (i), a figure standing or advancing holds 

 in the left hand a trident-like object, which is probably to 

 be understood as a plant; though, like the curious symbols 

 on the Boghaz-Keui bas-relief \supra, pp. 513, 514), it 

 must be somewhat idealized. Certainly, it would seem 



» Based on Lectures delivered by Mr. ThomasTyleratthe British Musetm 

 in January 1888. Continued from p. 593. 



^ Archtrological Journal, Dectmber 1887. Prof. Sayce's paper is accom- 

 panied by an autotype representation of the seal. I Uiay here mention, also, 

 that impressions of this seal, as also of the Yuzg&t seal and the seal of 

 Tarkutimme, may be obtained at a sm.iU cost from Mr. A. Ready, of the 

 British Museum. 



