A friend in Pennsylvania writes: “Please give us a description of the transit of Venus, in The Chautauquan for January.”

We answer with the following:

At a meeting of the New York Academy of Sciences, at No. 12 West Thirty-first street, on the evening of December 13, Professor J. K. Rees, of Columbia College, gave the result of his observations of the transit of Venus, made at the college observatory. A large audience was present and listened attentively to the lecturer’s presentation of facts.

“I will only detain the Academy a few moments,” said the Professor, “in presenting the main points in the observations made at Columbia College on December 6. Most of the figures I will leave out. The station occupied was the roof of the unfinished observatory of the college. The telescope was placed in the southwest corner of the roof. This roof is extraordinarily strong and solid, the beams being of iron, twelve inches in depth. Solid brick arches spring from beam to beam. The height of the roof from the street is about one hundred and ten feet. The walls supporting the roof are four feet thick. An unobstructed view was had of the whole transit. The position of the instrument was only a few feet from the old observatory, so that we may take the longitude and latitude of our instrument from the American ephemeris—

Latitude, +40° 45' 23.1.

Longitude:—From Washington, -0h. 12m. 18.40s.

Longitude:—From Greenwich, +4h. 55m. 53.69s.

“The timepieces used were a mean time chronometer, No. 1,853, made by Parkinson & Frodsham, of London, England, and a sidereal chronometer, No. 1,564, made by Negus & Co., of New York City. The instrument used in the observations was an equatorially mounted refractor by Alvan Clark & Sons. Aperture 5.09 inches; focal length of object glass, 74.3 inches. The magnifying powers used were 48 on the first contact, 165 on the second and third contacts, and 95 on the fourth contact. The telescope was moved by clockwork, supplied with a Bond spring governor. In making chronometer comparisons the sidereal chronometer was left at the college and the mean time chronometer was carried to the instruments on which signals were to be received. The sidereal chronometer has the hours graduated to XII.”

Professor Rees had prepared, but omitted to give, an elaborate system of chronometer comparisons with the Western Union time signals and the Washington time signals. The object of the comparisons was to obtain the exact error of the chronometers used at the time of the observations. The Western Union time signals sound the local mean time at the City Hall of New York city. The longitude of the City Hall from Washington is 12m. 10.47s. Mr. Hamblet, in charge of the Western Union time system, gives the errors of the Western Union time signals as 1.11s. fast on December 5, noon; 1.35s. fast December 6, noon. The professor also omitted a table of observations and the times taken down at the instant by each of four recorders.

“Correcting the observed contact times,” he continued, “the following table was obtained:

“The observation of the first contact was interfered with by the clouds. Between the first contact and the second contact the light shining through Venus’s atmosphere was a fine sight. I should say that it first appeared to my eye when the planet was a little more than half way on the sun, and disappeared about a minute before the planet reached second contact.

“I might, perhaps, introduce here,” said the professor, drawing a circle upon the blackboard, “the meaning of the terms first contact, second contact, and so on. Taking this circle to represent the sun, Venus is a disc which is about one-twenty-first part the diameter of the sun, and by first contact we simply mean the instant when the disc Venus, approaching the disc of the sun, touches it at one point externally. The second contact occurs at the time when the disc of Venus just touches the sun internally. The third contact Is the instant when the disc of Venus just touches the disc of the sun internally on one side, and the fourth contact is the instant when it touches on the other side.

“The line of light,” the Professor went on, after his explanation, “marking out the portion of Venus’ disk not on the sun, changed its appearance considerably while my attention was fixed upon it. I first saw a faint curved line of light off of the sun, and apparently marking out the part of Venus’ disk not on the sun, this curved line being entirely disconnected from the sun. A little later this arc of light was lengthened to a semicircular thread and touched the edge of the sun, marking out the complete outline of the part of Venus’ disk not on the sun. The semicircular gold thread seemed to be an exact continuation of the dark rim of the planet. Finally this line broadened at the point where it touched the sun’s rim, or edge, and the summit of the arc disappeared. The wings of light thus formed were, at their base, not in the exact continuation of the dark outline of the planet. I watched for the repetition of these appearances between third and fourth contacts, but failed to see anything. The sky between the first and second contacts was much clearer of haze than between the third and fourth.

“At second contact I saw no indication of the black drop. The tangency of Venus’ and the sun’s discs was well seen. During the passage of Venus over the sun’s face I observed her disc with magnifying powers of 48, 95, 165 and 345, but saw no indications of an atmosphere. The disc of Venus did not appear to be uniform in blackness, but to be spotted with grayish or whitish matter, reminding one of patches of snow. This was seen under the different magnifying powers used.

“When Venus neared the third contact a very peculiar phenomenon was noticed. The preceding edge of Venus was seen to be darker than the central portion. Later the edge of the planet became of a bluish black color, and this extended around to the following edge. The phenomena connected with this were very distinct. When the planet was near third contact these appearances were not seen longer. Just before third contact a faint black drop was observed for a short time. It disappeared very quickly, and third contact was finely seen.

“The fourth contact was interfered with by the haze and clouds, and was probably called too early.”

The Professor added that he desired to express his acknowledgments for aid in the matter of timing and in keeping the clockwork of the telescope in order to the fourth year civil engineers of the School of Mines. Without their assistance it would have been impossible to collect the time data which rendered the observations of value. At the conclusion of his address he was warmly applauded.