44 



NATURE [March 9, 191 1 



1901, Astacus gammarus, T. Scott, Brit. Assoc. Hand- 

 book Nat. Hist., Glasgow, p. 330. 



1906. Astacus gammarus. T, Scott, Proc. Roy. Phys. 

 Soc. Edin., vol. xvi., No. 4, p. 116. 



1906. Astacus gammarus, Stebbing, Victoria Hist. Corn- 

 wall, Crustaceans, p. 269. 



We have now to consider the significance of these refer- 

 ences. There is general agreement at present that the 

 marine lobster and the river crayfish must stand under 

 separate generic names. The question is. Which of the 

 two has a right to that name .-Xstacus, which for many 

 years they enjoyed in common? Miss M. J. Rathbun 

 argues that this was determined in 1810 by Latreille, who 

 in his " Consid. g6n. sur les classes des Crustac6s," &c., 

 gives a " Table des genres avec I'indication de I'esp^ce 

 qui leur sert de type," citing for Astacus only Astacus 

 fluviatilis. How little Latreille intended by this choice of 

 an illustrative species to strip the lobster of its ancestral 

 title may be inferred from his remark in 1803 that the 

 astakos of Aristotle is evidently the marine lobster, and 

 from the fact that still in 1831 he retains lobster and cray- 

 fish together in the same genus. Suppose, however, that 

 in such matters a man's intentions are of no consequence, 

 and that only his actions count, the same rule will apply 

 in the case of Borlase, who in 1758 mentions only one 

 species of Astacus, and that the common lobster, thanks 

 to_ the fact that the river crayfish was not, and seemingly 

 still is not, found in the county of Cornwall. But really 

 the man to whom the restriction of Astacus is due was not 

 Borlase, nor yet Latreille, but William Elford Leach, who 

 in 1815 detached from it Nephrops for the Norway lobster, 

 and in 1819 Potamobius for the river crayfish. 



There is talk about lists of notnina conservanda. Lists 

 of exempla vitanda would be much more to the purpose. 

 Here is a specimen. Leach having previously restricted 

 Astacus to the lobster, Milne Edwards in 1837 unlawfully 

 transfers that name to the crayfish already named Pota- 

 mobius, and endows the lobster with the new name 

 Homarus, of which it was in no need. In 1852 Dana 

 (U.S. Expl. Exp., vol. xiii., p. 532) follows suit, although 

 acknowledging that "Leach has undoubted priority," but 

 for various fanciful reasons setting that claim aside. He 

 informs us that " in some recent English works the name 

 Potamobius has been substituted for Astacus, and Astacus 

 for Homarus," just as if it were the English works that 

 had committed the crime of substitution, and he winds up 

 his argument by saying, " There seem, therefore, to be 

 reasons enough for rejecting Leach's names, if it is of no 

 weight that they remained for thirtv years unrecognised 

 by British authors." Yet John Obadiah Westwood was a 

 British author. 



Then Huxley in 1881 ("The Crayfish," third edition, 

 p. 13) tells us that Astacus was retained for both lobster 

 and crayfish until Milne Edwards (in 1837) called the 

 lobster Homarus. "At the present time, therefore," he 

 continues, " while the recognised technical name of the 

 crayfish is Astacus fluviatilis, that of the lobster is 

 Homarus vulgaris,'' though he admits that by astakos 

 the Greeks, ancient and modern, mean the lobster and not 

 the crayfish, and Huxley himself, while ignoring Leach's 

 Potamobius, accepts and defines (pp. 252, 256) a family 

 Potamobiidae. In 1888 Spence Bate (Challenger Macrura, 

 p. 192) follows in the wake of Dana, with some addi- 

 tional statements, of which my references will supply a 

 sufficient refutation. Thus these distinguished men bolster 

 up one another in wrong-doing, and feeblv lament the 

 supposed necessity of doing wrong. At a time when 

 British natural history was at a very low ebb, and natural 

 history at the British Museum had little to be proud of. 

 Leach suddenly threw lustre alike on that institution and 

 on the science of his country. Need we be surprised if 

 John Edward Gray and Adam W'hite and James Sowerby 

 felt the honour of Leach bound up with that of the great 

 museum to which they also belonged? They followed the 

 lead of the famous Westwood in vindicating the claims of 

 Leach. For English-speaking carcinologists on either side 

 of the Atlantic now to aid and abet in the transference of 

 Aristotle's Astakos and Leach's Astacus to a different 

 genus will be unscholarly and unpatriotic, as well as a 

 needless breach in the law of priority. 



Thomas R. R. Stebbing. 

 Tunbridge We'ls. Februarv 24. 



NO. 21:;$, VOL.' r.cii 



Time Accuracy in M«gr.etic Kegistration. 



Some contributions by Dr. Bauer and Mr. P^aris in the 

 last volume of Terrestrial \fagnetism have given rise to .1 

 number of letters in this journal concerning the startii.. 

 times of magnetic disturbances and the accuracy in tl, 

 determination of time on magnetograms. Mr. Walker (No 

 2147, p. 236) points out that the accuracy is augmcnttd 

 by interrupting both curve and base line. This is evident 

 the beams of' light reflected by the various mirrors of tl 

 variometers towards the horizontal cylindric lens have, : 

 general, different inclinations, the spots of light on tl 

 paper have different heights, so that the interruptions ; 

 different traces do not lie on a line perpendicular to th> 

 base line. Dr. Krogness (No. 2145, p. 171) desires rapi'l 

 registering with automatic time marks upon the cur\ 

 itself, in order to solve the question of simultaneity <• 

 non-simultaneity of the abrupt beginnings of magnet! 

 storms for different parts of the globe. 



F"or a number of years, an arrangement answerinj^ D 

 Krogness 's wishes has been applied at the Meteoro! 

 Institute at De Bilt (Netherlands) ; the method was de^ 

 for the first time in the Annuary B. for 1905, and rcct;ntly 

 in Terrestrial Magnetism (vol. xv., p. 31, 1910) in a com- 

 munication concerning the magnetic storm of September 

 25, 1909. By means of a contact clock, the circuit of a 

 battery is closed for two seconds every minute ; the curren' 

 illuminates a little glow lamp, the filament of which ' 

 straight and placed vertically. This filament takes tli 

 place of the illuminated slit in the usual arrangement ci 

 an Adie magnetograph ; its image, about i mm. wide , 

 would be formed in the plane of the paper. Just in front 

 of the paper, however, a screen with narrow, horizontal 

 slit is mounted ; accordingly, only the light admitted 

 through the slit falls on the paper, and we get a little 

 line or spot about J mm. long and I mm. wide. Every 

 minute such a spot is formed ; an hour corresponding to 

 15 mm. of base line, the recorded curve consists of a 

 series of points with a mutual distance of J mm. Another 

 contact lights the glow lamp every twenty minutes for four 

 seconds ; this contact falls between two minute-contacts, 

 and is convenient in reading the time. The correction and 

 the rate of the contact clock, and consequently the times 

 of the contacts, are exactly known ; the moments of the 

 twenty-minute contacts are om., 20m., and 40m. Greenwich 

 mean time. 



On quiet or moderately disturbed days the trace look?; 

 at first sight as a continuous curve ; at times of larji'T 

 disturbances the points are further apart. With the u-u.if 

 arrangement, in strongly disturbed parts the trace beconus 

 very faint, or is sometimes altogether lost ; this drawback 

 may be avoided by taking a wide slit, but then many 

 details in quiet or less disturbed parts of the curve are 

 lost. The new method of registration enables the varia- 

 tions to be followed exactly from minute to minute in all 

 circumstances ; it must be granted, however, that some 

 details, e.g. rapid oscillations of small period, are not 

 exactly reproduced by this method. 



The contacts being given once every minute, the 

 beginning of a disturbance, which, as a rule, falls betweenj 

 two contacts, is known with an accuracy of J minute^ 

 the uncertainty may be reduced, however, to i, J, or i/a 

 minute by giving the contacts 2, 3, or n times a minute 

 there is no objection against doing so, only the vek)ci| 

 of registration should be taken greater 2, 3, or n tir 

 respectively. 



It is evident that the method described shows soatf 

 analogy with that for seismic registration; here too 

 time mark is given generally once a minute by a contact 

 clock. These clocks being kept for sale, among othersi 

 by the manufacturers of seismographs, the arrangement ol 

 magnetic registration in the manner af>plied at De Bilt is 

 a rather easy matter. For the solution of various problems 

 recently advanced — simultaneity or non-simultaneity of th^e 

 abrupt beginnings of magnetic storms for differerit 

 elements, direction and velocity of propagation, and 

 character of disturbances, &c. — the providing of a number 

 of stations, spread over the globe in an aporopriatt 

 manner, with registering apparatus of the kind described, 

 would undoubtedly yield important data and results. 



G. VAX DlJK- 



Meteorological Institute, De Bilt, February 21. 



