November 28, 1890.] 



SCIENCE. 



303 



inches, the re-action was inhibited altogether. The distance of the 

 stimulus as apprehended by the eye, therefore, instead of giving the 

 increased motor excitement which we require, rather diminishes 

 it, and makes the need for some other explanation all the more 

 imperative. 



It appears, therefore, that the element needed in consciousness 

 to explain the facts cited in my former letter is some kind of a 

 difference in sensation corresponding to the outgo of the nervous 

 current into tlie right arm, be it as vague, subconscious, and un- 

 worthy of the name of " memory " as you please; that is, I still 

 think that my experiments support the traditional doctrine. On 

 any other theory, right handedness would have been developed 

 independently of effort. J. Maek Baldwin. 



Toronto, Ont., Nov. 18. 



Mount St. Elias. 



It is with great reluctance that I retui-n to the subject again, 

 but I beg to be permitted two statements in regard to the matter 

 recently a subject of discussion between myself and Professor 

 Heilprin in your columns. 



In the first place, I did not " unfavorably criticise " Professor 

 Heilprin's " work in Mexico." I merely pointed out that he as- 

 signed a weight to the observations which his equipment afforded 

 which that class of instrument (viz., a pocket aneroid) is not en- 

 titled to, and that the result of such observations (as to the accu- 

 racy or inaccuracy of which I raised no question) is not determi- 

 native within the limits he assumed. 



In the second place, discussion, in order to be profitable, espe- 

 cially in such matters as measurements and methods, must be just 

 and accurate as well in the representation of an adversary's posi- 

 tion as in the statement of one's own. In cases where the mutual 

 recognition of this obvious truism is impracticable for any reason, 

 I feel that it is better to cease the discussion, even though it 

 leaves me apparently worsted in the argument. As a matter of 

 fact, Professor Heilprin's understandins; of the work printed in 

 the St. Elias report (" Coast Survey Report for 1875 ") is hopelessly 

 inaccurate and confused; and to that report, therefore, I refer 

 those who are competent to judge of such matters, and may care 

 to possess themselves of the facts in the case. 



Wm. H. Dall. 



Smithsonian Instiiution, Nov. 22. 



Annular Phase of Venus. 



An opportunity of observing an unusual, if not remarkable, phe- 

 nomenon will soon occur; and I wish to call the attention of as- 

 tronomers to it, as another opportunity will not present itself until 

 after the lapse of eight years. This phenomenon may be conven- 

 iently called the annular phase of the planet Venus, though it 

 be produced not by reflected light only, as in the ordinary phases 

 of the moon, but partly also by the refracted light of the sun, 

 which has passed through the planet's atmosphere This phase I 

 unexpectedly witnessed tvventy-f'^ur years ago under the follow- 

 ing circumstances: — 



I desired to observe the prolongations of the cusps of the ores- 

 cent of light, mentioned by several writers, and which I after- 

 wards found had been observed by Madler in May, 1849, and used 

 by him to obtain the amount of refraction in the atmosphere of 

 Venus; but I had not then read his paper on the subject, and was 

 unacquainted with bis formulas. 



It was well known, that, if Venus and the earth at any time 

 occupied certain relative positions in their orbits, they would re- 

 turn very nearly to the same points, after an interval of eight 

 years less two and a half days. It was also well known that Ve- 

 nus would transit the northern part of the sun during the forenoon 

 of the 9th of December, 1874 (civil day at Greenwich), and would 

 transit the southern part eight years less two and a half days later, 

 or during the afternoon hours of the 6th of December, 1883. It 

 was therefore evident that it would pass north of the sun, and 

 very near it, eight years less two ami a half days before the first 

 of these transits, and would approach nearest to the sun about 2 

 P.M. (Greenwich time) on the 11th of December, 1866, least dis- 



tance of centres being about 88' of arc. I therefore prepared to 

 observe the planet on the forenoon of that day. 



My observations were made in the open air, on the grounds of 

 the College of Charleston, with a telescope presented to the college 

 many years ago by William Bucas, Esq. This telescope is a re- 

 fractor by Troughton & Simms, 5 feet focal length, 3f inches 

 aperture, eye pieces used magnifying 70 and 130 diameters. I so 

 placed my telescope that the apex of the north gable of the library 

 building, 23 jards distant, screened its object-glass from the rays 

 of the sun; and the planet was easily found and distinctly seen 

 above the roof of the library, least distance of nearest limbs about 

 23'. To my surprise, even astonishment, I saw not merely two 

 cusps prolonged, lut the whole circumference completely en- 

 lightened, the disk of the planet surrounded by a ring of light, 

 broadest on the side nearest to the sun, narrower but quite bright 

 on the opposite side. To have additional testimony to this fact, I 

 immediately called to witness it Messrs. E. T. Frost and W. St. J. 

 Jervey, two students in my astronomical class. They at once 

 recognized the illuminated circumference, and said that it resem- 

 bled in form the annular eclipse of the sun in October, 1865, 

 which they had seen in this city in the preceding year. As said 

 above, I was at this time unacquainted with Madler's observa- 

 tions and formulae, and, not having seen any intimation of the 

 possibility of such a phenomenon, it took me wholly by surprise. 

 I continued to watch the planet from 9 to 11 a.m , when the 

 library building ceased to be available as a screen. This interval 

 includes the instant of nearest approach of centres, which occurred 

 about 9.30 a m , Charleston mean time. 



As far as I can learn, the only other persons who saw the phe- 

 nomenon at that time were Professor C. S. Lyman of New Haven, 

 Conn., and a few of his friends. In his equatorial of 9-inch aper- 

 ture he saw the annulus or ring on the 10th completely formed; 

 but the line of light on the side farthest from the sun was slender, 

 faint, and only seen by glimpses. He saw it again on the 13th, 

 but did not attempt to observe it on the 11th, the day of conjunc- 

 tion, when I saw it as a brilliant ring of light. He doubtless would 

 have succeeded perfectly if he had abandoned the equatorial, 

 which could not be screened, and used a more portable telescope, 

 with some building as a screen. 



In 1874 I watched the planet at intervals from the 30th of No- 

 vember to the 13th of December, the transit taking place on the 

 night of the 8th and 9th, Charleston civil time. On the 3d of 

 December I saw for the first time during this interval the distinct 

 prolongation of the cusps, and watched their increase from day to 

 day until the 8tb, making eye-estimates of the number of degrees 

 in the enlightened portion of the circumference, as I had not effi- 

 cient means for making micrometer observations. On the 8th 

 and the 9th I fully expected again to see the annular phase, but 

 failed entirely to find the planet on both days There were no 

 clouds, at least not sufficient to entirely prevent observations, but 

 there was a dense haze, and the region near the sun was strongly 

 illuminated. 



At this transit Mr. Lyman was more successful than myself, 

 making good micrometer observations of the enlightened portion 

 of the circumference, and seeing distinctly the illuminated ring on 

 the 8th, the day before the transit. On the 9th he was, like my- 

 self, wholly unsuccessful in finding the planet, but on the follow- 

 ing days continued his micrometer measures. The results of these 

 observations he published in the American Journal of Science and 

 Arts for January, 1875, with the amount of refraction in the at- 

 mosphere of Venus deduced from his observations, and also Mad- 

 ler's formulae 'oy which it was deduced. 



In December, 1882, the weather was so unfavorable on the day 

 of the transit, the 6th, and for several days preceding and follow- 

 ing, that I made no attempt to observe it before and after con- 

 junction, and no accounts of the observations of others have 

 reached me; but the scientific periodicals to which I have access 

 are so few, that it would be unwarrantable to say that none have 

 been made. 



The next opportunity for observation will occur eight years less 

 two and a half days after the last transit, that is, on the 3d of 

 December next, when the least distance of centres will be about 

 35', at about 5.30 P.M., Greenwich civil time. As Venus will 



