July 26, 1888] 



NATURE 



291 



should. The orderly and effective administration of 

 justice, the weight which should be attached to judicial 

 decisions, the economy of public time, and, we would 

 add, the self-respect of scientific men, and the best 

 interests of scientific discovery, all call loudly for some 

 such reform as that here suggested. 



LA NGLE Y : S NEW AS TRONOM V. 

 The New Astronomy. By Samuel Pierpoint Langley, 

 Ph.D., LL.D. Illustrated. (Boston: Ticknor and 

 Co., 1888.) 



PROFESSOR LANGLEY'S beautiful book does not 

 appeal merely to the intellect. The senses have 

 their share in the gratification its perusal affords. .Every 

 turning of a page is a conscious luxury. Each touch of 

 the paper, in which the thickness of vellum is combined 

 with the polish of satin, flatters the finger-tips with a 

 bland caress. In texture, it compares with the paper on 

 which ordinary work-a-day scientific treatises are printed 

 as does a velvet-pile with a Kidderminster carpet. The 

 binding is in a corresponding style of lavish magnificence. 

 The illustrations have obtained the last perfection of 

 finish. 



Yet the excellence of their execution is for the most 

 part secondary to their intrinsic merit. Needless to say 

 that photographs figure largely among them. There is a 

 capital sunspot series by Rutherford ; there are specimens 

 of Pickering's stellar spectra ; besides several coronal 

 autographs, Mr. Common's inimitable Orion nebula, and 

 Rutherford's scarcely yet surpassed print of the moon. 

 Among visual delineations, we meet Bond's admirable 

 views of Donati's comet, Trouvelot's elaborate Saturn, 

 De la Rue's well-known Jupiter, above all, Prof. 

 Langley's own exquisite solar drawings. The surface 

 of the sun has probably never been so perfectly seen as 

 by him ; it has certainly never been depicted with such a 

 wealth of trustworthy detail. Some insight into one of 

 the sources of his success is afforded by the following 

 paragraph (p. 17) : — 



" The surface of the sun," he tells us, " may be com- 

 pared to an elaborate engraving, filled with the closest and 

 most delicate lines and hatchings, but an engraving which 

 during ninety-nine hundredths of the time can only be 

 seen across such a quivering mass of heated air as makes 

 everything confused and liable to be mistaken, causing 

 what is definite to look like a vaguely seen mottling. It is 

 literally true that the more delicate features are only 

 distinctly visible even by the best telescope during less 

 than one-hundredth of the time, coming out as they do in 

 brief instants when our dancing air is momentarily still, 

 so that one who has sat at a powerful telescope all day 

 is exceptionally lucky if he has secured enough glimpses 

 of the true structure to aggregate five minutes of clear 

 seeing, while at all other times the attempt to magnify 

 only produces a blurring of the image. This study, then, 

 demands not only fine telescopes and special optical aids, 

 but endless patience." 



'" Endless patience " is, indeed, a sine qud non in 

 nearly all departments of astronomy ; but it is not 

 always associated with the skill of eye and hand witnessed 

 to by the representations before us. Nor could they have 

 been brought to bear without instrumental accessories of 



a more than commonly high quality. The polarizing eye- 

 piece made at Pittsburgh must be one of the best ever 

 employed to blunt the keen edge of the solar rays. " By 

 its aid," our author remarks, "the eye can be safely 

 placed where the concentrated heat would otherwise melt 

 iron. In practice I have often gazed through it at the 

 sun's face without intermission from four to five hours, 

 with no more fatigue or harm to the eye than in reading 

 a book." 



The object of the work before us is to advocate the 

 claim of the " New Astronomy "—the astronomy which 

 studies the constitution of the heavenly bodies, as opposed 

 to that which determines their movements — to a larger 

 share of public interest, sympathy, and benefactions than 

 has hitherto been allotted to it. The appearance of the 

 eight chapters of which it consists in the pages of the 

 " Century " magazine, has doubtless already contributed 

 to promote that end. They are written in an eminently 

 popular style, and with much of that Transatlantic fresh- 

 ness by which many a jaded European palate is enticed 

 to renewed enjoyment of wholesome literary fare. They 

 profess to give only a sketch of the results so far attained ; 

 but it is a highly stimulating and suggestive one. 

 Intelligible to all, they should be welcomed by readers of 

 every grade of culture desiring to gain acquaintance, 

 almost without an effort, with some of the most surprising 

 encroachments ever yet made by the agile human mind 

 upon the vast realms of the unknown. 



The two most interesting, because the most original 

 chapters in the book, are those dealing with the "Sun's 

 Energy." Here Prof. Langley is more especially at 

 home ; his opinions carry all the weight that long medi- 

 tation and laborious research can give them ; yet they 

 are expressed not only without dogmatism, but almost 

 with diffidence. The higher value given to the " solar 

 constant" by his inquiries into atmospheric selective 

 absorption, have naturally obliged him to curtail the 

 " life" of the sun. During no more than eighteen million 

 years can the present rate of radiation — supposing it fed 

 by the shrinkage through gravity of the sun's substance — 

 have been maintained in the past. "We say 'present' 

 rate of radiation," our author continues, " because, so long 

 as the sun is purely gaseous, its temperature rises as it 

 contracts, and the heat is spent faster ; so that in early 

 ages before this temperature was as high as it is now, the 

 heat was spent more slowly, and what could have lasted 

 ' only ' eighteen million years at the present rate might 

 have actually spread over an indefinitely greater time in 

 the past ; possibly covering more than all the aeons 

 geologists ask for." 



This is of course perfectly true. There can be no 

 reasonable doubt that the sun was, in the initial stages of 

 its career, a comparatively murky luminary, rich in the 

 promise of future possession, but scantily distributing,, 

 because scantily supplied from, stores of light and heat 

 strictly tied up against the possibility of premature waste 

 for the benefit of generations to come, its heirs by entail. 

 But has there been no compensatory period of extrava- 

 gance ? Has our sun already passed through its " Sirian" 

 phase — if a Sirian phase be indeed an inevitable 

 " moment" in the existence of every star — or is it yet to 

 come ? The question cannot at present be answered ; 

 but until it is, estimates of the probable past duration, 



