November 20, 1891.] 



SCIENCE. 



2^9 



pressing through a break circuit clock moves the occulting 

 bar every second in such a way that the image of the star is 

 for the instant allowed to form on the photographic plate 

 behind this bar. The impression left by the star in transit 

 is a row of dots, which are afterwards developed in the usual 

 way. These dots are referred to the collimation axis of the 

 telescope by means of a glass reticule plate, ruled with one 

 vertical line. This plate is permanently fixed in the tube, 

 directly in front of the sensitized surface, and touching it. 

 After the star transit is over, the light from a lantern-is 

 allowed for a few seconds to fall upon the photographic 

 plate, which gives an impression of this reference line. The 

 row of dots which have just been photographed can not be 

 "fogged" by this light, as they are shielded behind the oc- 

 culting bar. After the, plates are developed they are meas- 

 ured by the aid of a micrometer. r 



In the Monthly Notices of the Royal Astronomical So- 

 ciety (LI., No. 9), Professor Barnard of the Lick Observatory 

 gives the result of his observation of Jupiter and his satel- 

 lites during the year 1890, made with the 13 inch equatorial. 

 One of the most interesting points in his paper is the fact 

 that he saw the first satellite elongated in a direction nearly 

 perpendicular to the belts of Jupiter. This observation was 

 made on Sept. 8, 1890, when both Mr. Barnard and Mr. 

 Burnham saw the satellite distinctly double. The distance 

 between the two images was about 1", and at a position an- 

 gle of 173°. Mr. Barnard gives two draA^ings, which repre- 

 sent the object as it appeared on two different dates. Two 

 «xplauatioas are suggested. The first is that the satellite at 

 the time of observation was crossed by a white belt parallel 

 to those on Jupiter, or, second, that the satellite is actually 

 double. We are strongly of the opinion that Mr. Barnard 

 has solved his problem in his first assumption. This is ex- 

 plained in an article written subsequent to the one from 

 which we have quoted. Ilis assumption is that the satellite 

 is crossed by a white belt, the remaining portion of the disk 

 being dark. Now, should an object of this character transit 

 a bright portion of Jupiter's surface, we would have the 

 «ifect of two small, dark disks close together, which would 

 appear round on account of irradiation and glare from such 

 a bright object as the large planet. As the little moon 

 passed across the face of Jupiter, the bright belt on the for- 

 mer would be lost in the bright surface of the latter. Now,. 

 if the satellite were to transit a dark portion of Jupiter's 

 surface, we would have the opposite effect, that is, a white 

 spot elongated in a direction parallel to the dark portion of 

 Jupiter's surface on the large planet. Mr. Barnard, in the 

 early fall, has reobserved these phenomena, and has found 

 both of the conditions above mentioned fulfilled. However, 

 these observations are very interesting, and only go to 

 show that some of our large telescopes can be put to a 

 good use in determining the markings on the satellites sur- 

 rounding Jupiter, and assist in determining their period of 

 rotation. 



The following are the positions for comet Tempel-Swift. 

 They are given for Paris midnight. 



Date. E. A. Dec. 



h. m. s. ° ' 



Nov. 23 32 52 41 +17 22 



25 23 4 6 18 27 



27 16 9 19 30 



29 28 48 20 33 



Dec. 1 23 42 1 -f-2t 34 



The comet will reach its m iximuin degree of brightness on 

 Nov. 23. 



The following are the positions for Wolf's comet. They 

 are given for Greenwich midniglit. 



Date. R. A. Dec. 



h. m. s. ° 



Nov. 18 4 32 53 —9 58 



20 31 35 10 38 



32 .30 16 11 14 



24 38 55 11 47 



26 37 35 13 19 



38 36 15 12 46 



^30 4 24 57 —13 11 



The comet has now reached its nearest approach to the 



earth. G. A. H. 



LETTERS TO THE EDITOR. 



#** Correspondents are requested to be as brief as possible. The writer^s name 

 is in all cases required as proof of (jood faith. 



On request in advance, one hundred copies of the number containing his 

 communication friU f>e furnished free to any correspondent . 



The editor loill be glad to publish any queries consonant with the character 

 of the journal. 



The Man of the Future. 



In his criticism of my conlribulioa to Science (Oct. 16) entitled 

 "The Man of the Future," which wag called forth by a former 

 letter from Dr. Langdon (No. 453), Mr. Snell has expressed his 

 views on the subject with great fulness and clarity {Science, Nov. 

 6). In several instances, however, the present writer can in no 

 way agree with him, and as those points of disagreement are of 

 prime i mportar.ce, they will be briefly dwelt upon here. Wlien 

 Mr. Snell says that " The problem of human progress seems to 

 have a fivefold aspect, physical, material, social, moral, and intel- 

 lectual; and it therefore involves questions belonging to sciences 

 as widely divergent as phyMology, technology, sociology, and 

 psvchology" (p. 359), we must believe that biologists, as a rule, 

 will not be fully in accord with him in the statement. Gi-anting 

 for the nonce that human progress has such a fivefold aspect, 

 surely the consideration of bis "physical" progress falls within 

 the science of morphology rather than that of " physiology "; the 

 " material" progress of man is quite secondary to the question at 

 issue, and it hardly seems to be encompassed by the restricted 

 science of "technology"'; finally, strictly speaking, ''psychology" 

 is but a department of physiology, as sociology is of biology, and 

 consequently both those sciences properly fall within the province 

 of biology for treatment. Erery biologist being more or less 

 familiar with the factors in operation in the premises, we take it 

 that the main object of the present discussion has to do more with 

 a speculation upon the probable morphology of the man of the 

 future, rather than it has to do willi a discussion of the aforesaid 

 factors, though undoubtedlj' in some instances it will be desirable 

 to make somewhat extended reference to them. 



As ilr. Snell remarks, he has not far to seek to find excellent 

 authority to support his statement that " Although in the sub- 

 human state the environment may have made the man, in the 

 human state the man, generally speaking, makes his environ- 

 ment." But surely if this factor be in operation at all, which I 

 do not fully deny, it is purely an exceptional one. and by no means 

 the nile. In our estimation, it has been very much overrated by 

 biologists. Take, for example, the ferine tribes the world over, — 

 in what way do the majority of them " make their environment " 

 any more than do the individuals in a community of beavers? 

 Many tribes, apart from the mere possession of speech, pass an 

 existence quite comparable with the lives led by some of the lower 

 mammals in a state of nature. Coming up to the so called semi- 

 civilized races of the earth, the same principle in the main still 

 holds true, although operative upon a somewhat higher plane. 

 One may as well assert that the average Turk "makes his environ- 

 ment," and we may ask in what particular ? If it be that he 

 makes it, I, for one. should like to see the experiment of his at- 

 tempting to step out of it. He probably would feel very much as 

 the monkey does on the hand-organ or in the menagerie. Even in a 

 highly civilized nation like our own, few there be indeed who really 



