112 



KNOWLEDGE. 



[May, 1903. 



further south than any previous record. The conditions 

 were very trying, the dogs all died, and the sledges had 

 to be dragged back to the ship, which was reached on 

 February 3rd. The party found that ranges of high 

 mountains continue through Victoria Land. Mountains 

 lO.OOO feet to 12,000 feet high were seen in latitude 82° 

 south, and the coast line continued at least as far south 

 as 88° 20', so that it seems that land stretches to the 

 Soutli Pole in a series of lofty mountains. Further 

 details of all this successful work, and of the many collec- 

 tions and observations made, will be eagerly looked for, 

 and it is hoped that an equally useful year's work will be 

 accomplished by the exjiedition in 1903. The "Discovery" 

 has lieeu revictualled by the '' Morning," and will winter 

 again in tne Antarctic. Lieutenant Sliackletou has retvuTied 

 in the " Morning " owing to his health, which suffered 

 greatly owing to the privations and hardships of the sledge 

 journey. Tjieutenant Mulock has taken his place. 



Eabthquakic in the Midlands. — The eartlnjuake felt 

 throughout the Midland counties on March 24th was not 

 one of the first magnitude, even for this country. It 

 resulted in but little damage to buildings ; though its 

 strength only fell short of tbat necessary for thro\ving 

 down a few chimneys or cracking the walls of houses. 

 The area disturbed by it includes the whole of Derbyshire 

 and Staffordshire, and a very large part, possibly all, of 

 the adjoining counties. The shock was felt as far north 

 as Preston, Lancaster, Leeds and Harrogate ; to the east, 

 it was percej)tible at Grantham, and to the south, it is 

 said, at Evesham ; that is, over an area of about 13,500 

 square miles. The position of the epicentre is not yet 

 determined, but it will probably be found to lie at no 

 great distance from that .part of Dovedale which lies west 

 of Matlock. Britisli earthquakes seldom last more than 

 ten or fifteen seconds, but the duration of the recent shock 

 must have been over, rather than under, half a minute. 

 This was due to its division into two distinct parts, 

 separated as a rule by an interval of a few seconds. On 

 this point, the personal experience of observers is corrobo- 

 rated by seismographic evidence. An interesting record 

 of the earthquake was given by one of Prof, Omori's hori- 

 zontal pendulums installed in Binningham, and shows 

 clearly two large oscillations, the total duration of the 

 shock, including the initial and final tremors, being about 

 one minute. The earth-waves, according to Dr. E. Wiechart, 

 were also registered at Gottingen, which lies about five 

 hundred miles from the centre of disturbance. — C. D. 



j^oticc g of B ooftg. 



"Prohlems in Astroi'IIYsics." By Miss Agnes M. Clarke. 

 (A. and C. Black.) lUustrated. 20s. net. — It is the custom in 

 England, in every great bu.siness firm, to go over the accounts 

 periodically, to balance the gain and loss, to take stock of the 

 assets of the company. The principle of a " periodical stock- 

 taking " is no less a sound one when applied to a science than 

 to a business concern, but it is less often put in practical 

 working : and we feel proud that it is an English astronomer 

 who has undertaken and carried through the audit for the most 

 exact of all the sciences. 



Miss Gierke's " Problems in Astrophysics" is indeed a great 

 astronomical stocktaking. She lays jilain before us the capital 

 of our knowledge. She shows what are the sound branches 

 from which advancement and profit may be expected. Slie 

 exposes the unsound principles whose practice can only mean 

 disaster, the theories so rigid and complete that they cannot 

 expand to include new facts, and so impede progress. " Finality 

 means stagnation." She writes down unsupported speculation 

 as of no value whatsoever. '' The ' floating of an idea ' in the 

 mind does not constitute knowledge; and a speculation is only 

 valuable when it offers a definite starting point for practical 



research." She discounts any complex hypothesis " which raises 

 more difficulties than it removes." 



The book is divided into two parts. The second deals with 

 the problems of sidereal physics; with those presented by various 

 types of stars; with variable stars of all kinds; with spectro- 

 scopic binaries; and with nebulse, " white " and " green." Our 

 sun is a true member of the sidereal system, but from his 

 proximity to us we can study him in detail as we cannot 

 remoter suns, and so another series of problems connected with 

 the solar surface and surroundings is piesented in the first part. 

 Though these two parts are for convenience treated separately, 

 essentially the >ame problems enter into both, and a question in 

 the one may find its answer or its corollarj' in the other. 



In the first part it may be said that all problems lead up, 

 more or less directly, for their solution to two questions. 

 AVhat is the cause and law of the sun's periodicity V What are 

 the natures and laws and conditions in the sun's surroundings V 

 These two questions are not distinct, they are bound u]) with 

 each other, and the answer to one will certainly throw light on, 

 if it does not completely solve the other. And is the first 

 question solvable ? Probably, if the law of periodicity be due 

 to an external cause, but Miss Gierke believes it is not so due. 

 The cyclical changes of the sun may be inherent, or "may simply 

 characterise a stage of growth, and prove liable to modification 

 and effacement. The study of variable stars will perhaps help 

 to guide ideas as to the probabilities of the case." So Miss 

 Gierke states the case and leaves it. It is indeed a hard problem 

 to ])ierce below the sun's photosphere and understand the 

 conditions imposed in a state so unattainable in our earthly 

 experience. And here we must express regret that Miss Gierke 

 has omitted all discussion of both planets and comets on the 

 plea that they " belong to the theoretical and descriptive depart- 

 ments of the elder celestial science." In Jupiter we have a 

 state of things that bears directly on the question of the solar 

 surface markings, of their periodicity, and of their connection 

 with rotation. 



In the second part, Miss Gierke assumes that time is the 

 principal factor in the evolution of the type of a star ; other 

 factors, such as mass, modifying but not determining the type. 

 The order of succession of the four chief families, she says, 

 leaves little room for doubt. Xebulae are the matrices of stars; 

 of these are, first, helium stars; then these pass by fine gradations 

 into Sirian : the Sirian by turn into solar : and these again into 

 stars with fluted spectra. It is assumed that photospheres of 

 helium and Sirian stars are " unveiled," and that those of solar 

 are "veiled," but this seems scarcely axiomatic; similarly the 

 assertion, on Duner's authority, that the absorption in sun- 

 spots is gaseous, namely that there is no increase in "general 

 absorption " in the umbra, is by no means proved to hold good 

 at all times and in all spots. By variable stars, the question of 

 the sun's periodicity is presented again in a more acute form, 

 and the constitution of "green" nebulaj raises many points that 

 urgently call for elucidation from laboratory experiments. 



It is a veritable tour de force, to have brought out two such 

 books as the fourth edition of " The History of Astronomy in 

 the XlXth Century," so largelj' a new work, and " Problems 

 in Astrophysics " within a few months of each other. We 

 must confess to having opened the second of the volumes with 

 a certain amount of trepidation ; the first was of such a high 

 order that it did not seem possible that Miss Gierke's strength 

 would permit her in so short a period to produce a work of even 

 equal excellence. But of her three great works, " The System 

 of the Star-s," "The History'' and "Astrophysical Problems,'' we 

 can unhesitatingly affirm that the latest is of even more value 

 and is the outcome of even profounder thought than its two 

 predecessors. There is one defect for which the publishers are 

 to blame. Miss Gierke's book is emphatically one that will not 

 be placed in that bookcase which is never opened. Is it right 

 to issue such a standard book with its pages uncut, so that when 

 the paper knife has done its work, the edges form an ideal 

 lodging for the dust and microbes of the world':* 



"°An IXTKOllUCTION TO Gk.LICSTIAI. MECHANICS." By F. R. 



Moulton, PH.D., Instructor in Astronomy in the University of 

 Chicago. (Macmillan.) — This work will be of very great assist- 

 ance to those students of Formal Astronomy (to use a particu- 

 larly happy phrase of IJr. Moulton) who wish to connect 

 mechanical and physical causes with their observed phenomena. 

 In a book numbering less than 4(M) pages, and dealing with a 

 subject so wide and so aljstruse, it has been necessary to assume 



