April 15, 1909J 



NA TURE 



193 



Principal Davis's little book consists of two parts. 

 The first, devoted to plants, gives an admirable resume 

 of their being and well-being, their varieties and 

 adaptations. The second treats in systematic fashion 

 the chief groups of animals, and, though less " bio- 

 logical," is well arranged and packed with informa- 

 tion. The illustrations throughout are most attrac- 

 tive, and the plan of the te.xt well designed. For 

 schools the book is certain to be found useful, and 

 the only faults we have to find with it are the attempt 

 to explain everything and the absence of any attempt 

 to give practical directions for the simplest experi- 

 ment. The first is certainly a serious mistake. The 

 too readv application of the magic word " protection " 

 in regard to colouring, for example, is frequently un- 

 justified, and the bald statement, e.g., that birtfs are 

 derived from reptiles that rose on aeroplanes, is at 

 least a daring one when its speculative nature 

 is not hinted at. Phylogenetic speculation should be 

 rigorously excluded from elementary teaching. 



The absence of experimental advice is a too common 

 drawback to books of this kind, and yet perhaps no 

 method is equal to this one in value. With animals 

 there is always a difficulty in suggesting an experi- 

 ment that has not an unnatural or even a cruel look, 

 but plants are. made for experiment, and a training 

 in that branch of work is one that can be effected 

 cheaply and conveniently. These defects do not, 

 however, prevent this little book from being a fund 

 of attractive information on both animals and plants. 

 The subject-matter is highly compressed, and teachers 

 will find that a single paragraph has to be expanded 

 and illustrated before it can be properly grasped bv 

 their pupils. Such compactness is, however, inevitable 

 in a work of such small size and wide compass. 



INTERNATIONAL CHART OF THE 



HEA YENS. 



'T'HE permanent committee of the Astrographic 



'■ Congress of 1887 will meet at the Paris Ob- 

 servatory, April 19 to 24. Our readers will remem- 

 ber that the great international undertaking — the 

 Carte du Ciel — was inaugurated at a congress held 

 at Paris in 1887. No astronomer who attended the 

 meeting can forget the man whose name will ever 

 be associated with that work — Admiral Mouchez, 

 then director of the Paris Observatory. But for his 

 earnest and sympathetic character and genial influ- 

 ence it is doubtful if this great work could have been 

 launched at all ; it certainly could not have been so 

 w-ith the same prospect of success without his tactful 

 and energetic cooperation. 



At that congress a scheme was prepared and 

 H permanent committee appointed to carry the 

 work into execution. The committee in question 

 consisted of eleven members, selected by vote, to- 

 gether with the directors of observatories cooperating 

 in the work whose names did not appear in the 

 original list. This committee met at intervals of 

 from two to four years at Paris until the year 1900 

 inclusive, but since that time no further meeting of 

 the permanent committee has taken place, and we 

 shall see presently how urgent is the need for the 

 coming meeting. 



Broadly speaking, the programme entrusted to the 

 committee was as follows : — 



(i) To construct charts of the entire sky, each map 

 measuring 2°X2°, and containing all stars to the thirteenth 

 magnitude. 



(2) To catalogue the exact positions and magnitudes of 

 all stars to the eleventh magnitude. 



At first the chart appeared, even to some astro- 

 nomers, to be the more important object to be 



NO. 2059, ■^'OL. 80] 



realised, but there has been a growing conviction 

 that, for the broad fundamenta of astronomy, the 

 catalogue, though by far the more laborious, is in- 

 finitely the more important of the two objects. 



The chart, it is true, preserves a permanent record 

 of the state of the sky for a mean epoch about 

 1900, to which reference can be made, as occasion 

 may arise, in connection with variable stars and the 

 appearance of new stars, and, after special measures, 

 it will yield the places of stars fainter than the eleventh 

 magnitude which may be suspected of large proper 

 motion, &c. 



But, with the completion of the catalogue, astro- 

 nomers will be provided with absolute places of all 

 the stars down to the eleventh magnitude, and this will 

 enable them, when the work has been repeated after 

 a suflicient interval, to derive the proper motions of 

 all stars to the eleventh magnitude in the most simple 

 and direct manner, and so to investigate such prob- 

 lems as the precession, the solar motion in space, 

 star-drift, &c., and to discuss the general problems 

 of sidereal astronomy with a completeness unattain- 

 able in any other way. 



By the complete execution of our present pro- 

 gramme we lay upon astronomers of the future the 

 moral compulsion to execute a similar work, say, 

 one hundred years hence, and, in addition, to derive 

 from the three or four millions of proper motions so 

 obtained the broad cosmical conclusions which must 

 follow from the proper discussion of these motions. 



This, surely, is a large enough task to bequeath to 

 futurity— a noble bequest indeed if it be left in the 

 complete, permanent and accessible form of a printed 

 catalogue of positions and magnitudes. To leave it 

 in any other form would be to endanger the per- 

 manent value of our work by throwing such an 

 undue share of labour upon our successors as almost 

 to justify them in refusing to utilise what we have 

 done. 



The work of the chart and of the catalogue was 

 originally divided amongst sixteen observatories, and 

 naturally has proceeded at different rates in different 

 observatories according to their opportunities, the 

 varied energy of their directors, and the means at 

 their disposal. Practically the work has now con- 

 tinued for nearly twenty years, but, of course, a 

 good deal of time was lost at first in the construction 

 of instruments and in experimental research before 

 definite routine work was commenced. 



But whilst some of the observatories have nearly 

 cornpleted their share of the work, others are far 

 behind, and it will be an important duty of the 

 present meeting to inquire into the progress of each 

 zone, to divide up the unexecuted work amongst the 

 more active observatories, and to take such other 

 steps as are necessary to bring the whole to an 

 early and satisfactory completion. 



In a circular letter addressed to the directors of 

 the cooperating observatories and to others invited 

 to attend the present meeting, M. Baillaud, director 

 of the Paris Observatory, and president of the per- 

 manent committee, makes the following requests, 

 viz. : — 



(a) That each observatory which, up to the present time, 

 has cooperated in the work, shall prepare a report show- 

 ing the amount of work done, not only in taking the 

 plates, but in the measurement, reduction, and publication 

 of the results. 



(8) That those astronomers who find themselves in a 

 position to aid in the completion of zones which have fallen 

 into arrear either in the matter of taking the plates or in 

 their measurement and reduction, should intimate their 

 readiness to assist in the work. 



In entering into the whole question of the present 

 state of the work, and taking such farther steps as 



