December 31, 1891] 



NATURE 



197 



Mr. T. C. Hepworth and Mr. W. T, Bashford trace the 

 history and describe carefully the various processes of 

 photography. Mr. J. S. Keltie has an excellent article on 

 Polar exploration, illustrated with a North Polar and a 

 South Polar chart. A short but very good paper on 

 protoplasm is contributed by Mr. J. A. Thomson ; and 

 Prof. Sorley makes the most of the few pages set apart 

 for psychology. Rain is discussed admirably by Dr. 

 Buchan, and the rainbow by Mr. W. T. Omond. Reflec- 

 tion and refraction are dealt with by Dr. Alfred Daniell. 

 The main facts relating to the Red Sea are presented 

 by Dr. John Murray ; and Dr. Hugh R. Mill sets 

 down all that is likely to be wanted by students who have 

 occasion to refer to the article "River." Altogether, the 

 various papers we have examined may be commended as 

 in every way worthy of the high reputation secured for 

 the present edition by preceding volumes. 



La Place de V Homme dans la Nature. By T. H. Huxley. 



(Paris : B. B. Bailli^re et Fils, 1891.) 

 More than twenty years ago a French translation of 

 Prof. Huxley's well-known work, "Man's Place in 

 Nature," was published. The translator was Dr. E. 

 Dally. In the present volume this rendering is reissued, 

 and along with it are associated translations of three 

 papers in which Prof Huxley has presented his ideas on 

 various ethnological subjects. These papers have been 

 translated by Dr. Henry de Varigny, to whom Prof. 

 Huxley expresses thanks for the care he has taken to 

 represent clearly and faithfully the meaning of the 

 original. The volume will be very welcome to French 

 students who desire to understand the methods and 

 tendencies of English scientific thought. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of ^ \T\JVt.K. 

 No notice is taken of anonymous communications. 1 



Smithsonian Standards for Physical Apparatus. 



On the occasion of a scientific expedition of which I had 

 charge many years ago, the need of common standards of size for 

 the parts of different astronomical and physical instruments was 

 brought forcibly to mind ; for the instruments used, while of the 

 latest and best construction, were necessarily dismembered, and 

 then transported in fragments to their scarcely accessible desti- 

 nation by numerous independent bearers ; and if any accident 

 happened to any fragment of any piece of apparatus, it was 

 found, as a rule, that the whole was rendered useless, since it 

 could not be replaced from the like parts of other pieces which 

 were spared. The weapons of attack of the little scientific force 

 were, then, in one important respect, far inferior to those of 

 modern warfare, in that there had been no attempt to make 

 their parts interchangeable. 



My attention having been drawn to the matter, I was led to 

 examine astronomical and physical instruments in all cabinets 

 accessible to me, with a special view to this feature. I found 

 that, as a rule, no draw-tube, screw, or other piece from one in- 

 strument would fit the corresponding parts in any other, there 

 being no attempt to make them interchangeable even where 

 they came from the same maker. 



This experience must be confirmed by that of most others, 

 who will probably agree that thi-; is a cause of incessant, but 

 quite avoidable, loss and delay, even where apparatus is used 

 under ordinary conditions, and it has led to inquiry for some 

 scheme which would assimilate different parts of the work, not 

 only of the same, but of different makers. Some of the plans 

 suggested are well matured, and in themselves apparently com- 

 mendable, but all are too complex, the ambition of the authors 

 being, as a rule, to make them so complete as to cover all 

 possible demands of future progress. 



What has been wanted by many others doubtless is some 

 simple and practicable plan for immediate use, which shall yet 



NO. I 157, VOL. 45] 



be found in accord with the larger scheme which may be under 

 consideration hereafter. 



When it fell to me to meet the somewhat varied wants of the 

 Smithsonian Institution by a plan which should at least enable a 

 beginning to be made in the right direction, it seemed that this 

 should be with such simple and general conditions, that com- 

 mon consent to them might almost be counted on, at least on 

 the part of all ready to use the metrical standards. 



To provide for the immediate practical wants of this Institu- 

 tion, advice was sought of several of the best instrument makers, 

 and a considerable number of tubes and screws by English, 

 French, and German, as well as American makers were 

 examined to find out the sizes which long-established use in 

 these countries had shown to be practically convenient, and the 

 forms of screws which the best modern practice of scientific 

 instrument makers concurred in ; and this having been done, 

 dimensions having a metrical unit, and as near these sizes 

 as practicable, were adopted — not as a finality, but as a 

 beginning. 



In the hope that others may consider this very modest 

 attempt to be in the right direction, and that these standards 

 may fall into use for immediate needs, and thus tend to bring 

 about the adoption of that much more complete system of inter- 

 national standards which most will admit to be (at least in the 

 abstract) desirable, I beg leave to inclose a circular which has 

 been sent to all instrument makers employed by this Institution, 

 trusting that you may find it of sufficient interest to bring it to 

 the attention of the readers of Nature. 



S. P, Langley, 



Secretary. 



Smithsonian Institution, Washington, D.C., December 16. 



Circular to Instrtiment Makers. 



In all apparatus used by the Smithsonian Institution a series 

 of standard sizes for metal tubes and for the screws chased on 

 them has been adopted. The metric division is employed, and 

 all tubes ordered are to be finished to some even number of half 

 centimetres in diameter, unless this cannot be done without great 

 difficulty. The series of diameters and corresponding threads 

 to be used is, for a diameter of 



10 centimetres, 5 threads to a centimetre. 



9 „ 5 M 



7-5 .. 7 ,. 



6 „ 7 „ 



3 .. IS » 



When any new tube has to be ordered, it should be made one 

 of these diameters and chased with one of these threads, if this 

 can in any way be done. 



New eye-pieces are to be as far as possible made to fit the 

 three-centimetre plug gauge supplied by Pratt and Whitney, and 

 in fitting them to old work, this size is still to be adapted 

 wherever possible. The Institution is preparing standard plugs 

 and gauges of the diameters given above, and has on hand 

 chases of 5, 7, 10, and 15 threads to the centimetre. All screws 

 have the 60° thread, with flattened top and bottom. These it 

 will supply at first cost to any instrument maker engaged in its 

 work. 



Plug gauges are to be had of great accuracy and at moderate 

 cost from several standard tool makers. Those here referred to 

 have been made for the Smithsonian Institution by the Pratt 

 and Whitney Company of Hartford, Connecticut, and are 

 within a limit of error of two-hundred-thousandths of an inch 

 at 62° Fahrenheit. The hobs are from the same makers. 



Pigment in Yellow Butterflies. 

 Apropos of the interesting discussion on comparative pala- 

 tability and warning colours (Nature, November 19, p. 53 ; 

 November 26, p. 78), it may be of interest to your readers it I 

 restate in your columns some of the properties of the yellow 

 pigment contained in the wings of the common brimstone and 

 many other butterflies ; the possible significance of which in 

 conferring protective unpalatability is suggested by Mr. Beddard. 

 My paper on the subject, to which Mr. Beddard refers, was read 

 before the Chemical Society in June 1889 ; hut, being more or 

 less of a preliminary nature, it was published only in the 

 abstracts of that Society's proceedings (Abst. Proc. Chem, 

 Soc, vol. v., 1S89, p. 117 ; vide also Nature, vol. xl. p. 335). 



