4io 



NA TURE 



[August 30, 1 88b 



the structures found in the Appalachians are equally 

 characteristic of the Alps, and the more denuded 

 mountain chains of Central and Northern Europe. In 

 explaining the causes of regional or mechan : cal meta- 

 morphism, Dr. Reyer fully appreciates the importance of 

 the experimental researches of Tresca, Daubree, and 

 Spring ; while he fails not to point out the important 

 additions and confirmation of the theory of " mechanical 

 metamorphism," which are furnished by the microscopical 

 investigations of Lossen, Lehmann, and other recent 

 authors on the subject. 



Seismology, the study of earthquake phenomena, is 

 usually treated by the writers of text-books as a branch of 

 vulcanological science ; but we agree with the author in 

 regarding it rather as connected with the great move- 

 ments of earth-masses. It finds an appropriate place in 

 this work between the chapters dealing with dislocations 

 of the earth's crust, and those devoted to the great secular 

 movements of the earth's surface. 



In a work like the present, devoted to a discussion of 

 problems of the greatest difficulty, many of which are far 

 from ripe for solution, some of the views of the author 

 will be sure to challenge criticism and others to provoke 

 dissent. Every unprejudiced reader will admit, however^ 

 that Ur. Reyer's presentation of his views upon these 

 problems is characterized not only by much originality of 

 thought, but by a studious fairness of manner. The 

 citation of original authorities in every case is a most 

 praiseworthy feature of the work, and those writers from 

 whom the author differs have no cause to complain, as is 

 too often the case, that he has not even tried to understand 

 their arguments. Nowhere does there exist such a rich 

 storehouse of facts and observations bearing upon the great 

 questions of geology as in the volume before us, and we 

 cannot doubt that the completion of Dr. Reyer's important 

 work will mark an epoch in the history of the science, and 

 at the same time constitute an important starting-point 

 for further advances. J. W. J. 



A GUIDE TO THE LICK OBSERVATORY. 

 Hand-book of the Lick Observatory of the University 0/ 

 California. By Edward S. Holden, LL.D. (San 

 Francisco : The Bancroft Company, 1888.) 



THERE are two classes of readers to whom this little 

 book ought to be especially welcome — namely, 

 those who propose to visit California, and those who do 

 not so propose. Travellers will miss from it no useful 

 item of information. They are told where to lodge, 

 what to wear, how to get themselves conveyed to 

 their destination, what to look at and admire. They 

 are put, moreover, in the proper frame of mind for 

 approaching an astronomical sanctuary. The coldest 

 and dullest can hardly under such guidance remain 

 utterly apathetic and unintelligent. The general in- 

 terest of the work, on the other hand, is sufficiently 

 attested by a glance at the table of contents. It 

 includes a " Sketch of the Life of James Lick," the 

 founder of the Observatory, a history of the institution, 

 descriptions of the buildings and instruments, with sec- 

 tions on " The Work of an Observatory," " Telescopes,'' 

 " Astronomical Photography," " Clocks and Time-keep- 

 ing," and " The Principal Observatories of the World." 



On none of these subjects are there many, on some there 

 is no one entitled to speak with greater authority than 

 Prof. Holden. Nor is there a second astronomer in the 

 world whose utterances — so far as they are an index to 

 his intentions — are at present of higher moment to 

 science. The future course of observation largely de- 

 pends upon his use of the vast opportunities placed in his 

 hands. A colossal experiment is being tried at Mount 

 Hamilton ; its upshot will lay down the lines of astro- 

 nomical effort for many a decade to come. For results 

 govern the star-gazing, no less than every other section 

 of mankind. 



Prof. Holden vainly, we fear, seeks to disabuse the 

 public of its fixed idea that " an astronomer's business is- 

 to watch the heavens go by and to ' make discoveries.' 

 Exactly what these discoveries are," he goes on to say, 

 " is usually not stated, but unless a sufficient number are 

 forthcoming the astronomer is held to be blameworthy." 

 The Lick Observers, however, possess a unique advan- 

 tage in the value of their negative results. " What we 

 cannot see with our telescope, the most powerful of all, 

 in our elevated situation, the best in the world, need not 

 be looked for with inferior telescopes in less favoured 

 situations." 



Celestial photography is evidently designed to be 

 vigorously prosecuted on Mount Hamilton. " One of the 

 principal objects of the Observatory," we are told, " will 

 be to make a photographic map of the heavens, by means 

 of the large telescope and its photographic objective." If 

 carried out on the scale which appears to be indicated, 

 this will indeed be a gigantic undertaking. Its plan is 

 doubtless not yet definitely laid down, but exposures of 

 three hours are spoken of. On Mount Hamilton, two 

 hundred nights in the year — just double the low-level 

 allowance — can be counted on as fit for such work ; yet 

 even so, twenty-five years should elapse before the whole 

 sky could be once covered by plates each embracing four 

 square degrees, and exposed during three hours. And 

 the resulting priceless record would lose, unless obtained 

 in duplicate, great part of the value properly belonging 

 to it. 



The time-service of the Lick Observatory has been for 

 some time completely organized. Every railway-clock in 

 the Southern Pacific States is now regulated from Mount 

 Hamilton. Any watch in San Francisco can be set by 

 the beats of the Lick standard clock, rendered audible by 

 telephone at a distance of sixty miles. The time distri- 

 buted is the " Pacific standard," which is 6m. 343s. 

 faster than the Mount Hamilton local time. Numerous 

 plans and illustrations enhance the usefulness of the 

 " Guide to the Lick Observatory." A. M. C. 



OUR BOOK SHELF. 



Curve Pictures of London for the Social Reformer. By 

 Alex. B. Macdowall, M.A. (London : Sampson Low, 

 ]888.) 

 This little volume ought to be of great service to all who 

 interest themselves practically in questions relating to 

 social reform in London. It presents by means of 

 diagrams a large amount of trustworthy information about 

 population ; density of population ; birth, marriage, and 

 death rates ; early marriages ; death by disease ; suicides ; 

 drunkenness; licensed houses; apprehensions; felonies; 





