May 4, 1888.] 



SCIENTIFIC NEWS. 



429 



servant poured out the cat's allowance of milk, the fox would 

 run to the spot and walk about the saucer, well knowing that 

 none of the rightful owners would approach the defiled 

 locality. Day after day the cats lost their milk until the 

 stratagem was discovered, and the milk was placed in a spot 

 where it could not be reached by the fox. He was also very 

 successful in cheating the dogs of their food, achieving his 

 thefts by the force of superior intellect." F. P. P. 



A UNIVERSAL DAY. 

 The adoption of a universal day, as described in your last 

 number, would do away with a difficulty which, I believe, 

 puzzles many persons besides myself. I have never yet seen 

 a clear answer to the question, " Where, under the present 

 arrangement, does the day begin ? " For instance, I am 

 writing on the 24th of April, at noon. This particular date at 

 the meridian of Greenwich commenced twelve hours ago. At 

 Berlin and Vienna it commenced something like thirteen 

 hours since, and so the further East one travels the longer is 

 it since this particular date commenced, until one comes to 

 the meridian iSo" East of Greenwich, where it must be 

 exactly twelve o'clock 7nidnight of the sa77ic date. At one 

 minute past twelve noon, Greenwich time, it will be one 

 minute past twelve past midnight — that is in the morning — 

 at 180° East longitude. If to-day began at 180° East longi- 

 tude from Greenwich, it must end I So" 'West longitude of 

 Greenwich. The places just East of that meridian are 

 therefore only finishing the 24th of April, while, say New 

 Zealand, is just beginning the 25th. Here I am nonplussed. 

 As a matter of lact, I should like to know whether there are 

 places in the Pacific where the dates thus differ by twenty- 

 four hours. If so, are these places known ? For example, 

 are there places not far apart which if they published evening 

 newspapers to-day, would in the one case date those papers 

 the 24th, and in the other the 25th ? If so, where does the 

 dividing line run ? Thomas C. Dare. 



"THE SHELL-COLLECTOR'S HANDBOOK FOR THE 



FIELD." 

 In mere justification of my publishers and myself I may 

 be allowed, in equal fairness with your reviewer, to reply to 

 some criticisms made by him on the above manual in these 

 columns some three or four weeks back. I would point out 

 to him, in the first place, that as conchology is essentially a 

 field, and not a home, study, the title is not a misnomer, and 

 that had biographical descriptions of the various species been 

 included in the text it would have made the book an exceed- 

 ingly expensive one, and would altogether do away with the 

 purpose for which it was written, viz., simply as an identifica- 

 tion manual within the reach ot the pockets of all. In the 

 second place I. would refer him to the latter portion of the 

 preface, where he will find it stated that " the varieties des- 

 cribed include those which have been verified by the Council 

 of the Conchological Society or by myself," and these have 

 been sifted from the garbage made by those tyro variety 

 mongerers who do not yet understand the distinctions that can 

 be legitimately drawn between tjrpe-forms and varieties, and 

 who have had their futilities so well exposed by JVIr. 'Wood- 

 ward in the Zoologist, and by Mr. J. 'W. Taylor, in his recent 

 Valedictory address, as President to the Conchological 

 Society. It is to these spurious varieties that your reviewer, 

 when he talks of "errors and omissions" evidently refers, 

 but I may tell him that had I recognised them I had done 

 wrongly to myself, and had deserved the greatest amount of 

 censure that could be heaped upon me by all true and 

 scientific conchologists. To me Arion aier v. plumbea is but 

 a pale, and perhaps, a young, type, and not distinct enough 

 in colour to warrant a varietal name. While Limax arborum 

 was not named in my handbook as Lehmannia inarginata, 

 simply because the priority of the name has not yet been 

 recognised by the Conchological Society. The scoop was 

 not mentioned since it is, as yet, but new-fangled, and has not 

 not stood the test of time as the water-net and walking-s'^ick, 

 which the majority of us take when out on a collecting 

 excursion. J. W. Williams, M.A. D.Sc. 



WHAT KIND OF LEVER IS AN OAR? 

 The occasion for this question, which is raised in a letter 

 in Scientific News for March 2nd, arises from the circum- 

 stance that the power applied (the man rowing), and the 

 support for the oar in the rowlock, are both moved by the act 

 of rowing ; but the lever action of the oar can be conveni- 

 ently considered by substituting for the man a rope passing 

 over a stationary pulley upon shore, having a weight hung to 

 it equal to the pull of the man upon the oar. Taking the 

 lengths of the oar inside and outside the boat to be in the 

 proportion of i to 3 as in the above letter, and taking 3 ft. as 

 the distance the boat is propelled by each stroke of the oar, 

 and 4 lbs. as the resistance of the boat to the oar, then the 

 work done at each stroke is 12 ft. lbs. (4 lbs. x 3 ft.). Then, 

 taking first the case of the outer end of the oar being held 

 stationary by the water without any back slip, the inner end 

 of the oar will be moved 4 ft. in the stroke, as the rowlock of 

 the boat is moved 3 ft., and consequently the weight pulling 

 the end of the rope will descend 4 ft. in the stroke, and the 

 amount of weight required is 3 lbs. to the work of 12 ft. lbs. 

 (3 lbs. X 4 ft.). Now transfer the pulling from the shore to 

 the bow of the boat, so as to represent the action of the man 

 rowing, and the pulley will then be itself moved forward 3 ft. 

 with the boat during ithe stroke, and the rope will conse- 

 quently only pass over the pulley a distance of i ft. (4 ft. — 3 ft. ), 

 and the weights will only descend i ft. ; the amount of weight 

 required pulling the end of the rope is then 12 lbs. to do the 

 work of 12 ft. lbs. (12 lbs. x i ft.). The pull e.xerted by the 

 man rowing is therefore 12 lbs. to overcome a resistance of 

 4 lbs. in the boat, being a proportion of 3 to I, the same as 

 the proportion of the lengths of the oar outside and inside 

 the boat ; and the oar is in effect a lever of the first order, 

 having its fulcrum at the rowlock. 



In the case of the water yielding to the oar-blade, the 

 outer end of the oar will slip back a certain distance during 

 the stroke, instead of being held stationary by the water, and 

 the boat will consequently not be propelled the full 3 ft. at 

 each stroke, some of the power employed being e.xpended 

 upon displacement of the water by the oar-blade. 



W. 



ANSWERS TO CORRESPONDENTS. 



H. R. Co ..IBS. — We believe that Colatina can be obtained of 

 Messrs. Christy and Co., 155, Fenchurch-street. 



A. G. TiNDALL. — The only way to carry out the experiment 

 you wish to perform would be to look through a solution 

 of quinine at the ultra-violet part of the spectrum. We 

 do not know of any such ink. 



George Whitfield. — We can see no proof and believe that 

 this method is only approximately correct. Try it on a 

 very large scale. 



Racial Elements of the Russian Army. — Probably 

 the Russian army is the most heterogeneous in the world 

 so far as its ethnology is concerned. From the informa- 

 tion on the point just issued by the Russian Statistical 

 Department we learn that of the 227,906 recruits levied 

 in 1S85, the racial composition was as follows: — Russians, 

 169,052; Poles, 17,212; Bulgarians, 406; Tchecks, 12; 

 Lithuanians, 5,800 ; Letts, 3,424 ; Greeks, 155 ; Molda- 

 vians, 2,350; French, i; Germans, 3,572; Armenians, 

 142; Bohemians, 39; Georgians, 3; Jews, 10,011; 

 Karehans, 309 ; Tchouds, 20 ; Esthonians, 2,604 j Laps, 

 I ; Moravians, 1,707 ; Cheremissians, 704; 'Votiaks, 841 ; 

 Zyrians, 282 ; Permians, 68 ; 'Voguls, 5 ; Chuvachis, 

 1,529; Tartars, 4,508; Bashkirs, 3,017; and about 100 

 belonging to three other races or tribes. In all, then, 

 the Russian army comprises 32 different race, or at least 

 tribal, elements, among which it is noteworthy neither 

 Ossetians nor Circassians are represented, so far at least 

 as these recruits are concerned. 



