11th was only one second different from what it was on the 9th, so I did not apply any rate correction.

I computed the exterior ingress contact; and the interior contact I obtained by adding the difference given in the Ephemeris. Computed times, as well as those observed, are as follows:

In computing I used the latitude and longitude for Ogden given in the Ephemeris, though my place of observation was one and one-quarter miles east of the old observatory.

I expect to compute and observe the eclipse of June 6th, and will send the results, if they have any value.

W. C. PARMLEY.

P. S. (May 21.)-I have triangulated carefully the distances from the Latitude and Longitude Observatory Pier to the City Hall, and the distances are as follows to where my telescope was-6394 feet east and 69 feet north. These measures are probably correct within three feet. Mr. BOSTAPH was stationed about eight feet south of me. I find the marks on the pier slightly different from the values given in the Ephemeris. They are: Longitude 11° 59′ 54′′.64; latitude 41° 13′ 08′′.56. I do not know the cause of the difference.

OBSERVATIONS OF THE TRANSIT OF MERCURY, MAY 9, 1891, BY C. W. IRISH, RENO, NEVADA.

RENO, May 16, 1891.

PROF. E. S. HOLDEN: I have duly received yours of the 13th inst., and as you state your intention to publish my report of observations of the partial transit of Mercury made by myself on the 9th inst., by the aid of Mrs. IRISH as time-reader, I deem it best to rewrite said report and condense it as much as I can.

First contact came on while the sun's limb was very much agitated by puffs of cold air, coming from a southwest direction, and the first sign I saw of the planet was at 3" 54" 00 ̊.031, and I had, one and one-half seconds before this, been looking at the exact point of contact, but, owing to the remoteness of the sun's limb, did not see the planet. So I place the latter time at

3 53 58$.531±0.3, and believe that had it not have been for the agitation of the sun's limb I should have seen Mercury then, if not in contact, certainly about in that position. The notch, made at the former time, flashed, as it were, into sight upon a partial cessation of quivering in the air.

At 3h 55m 08.67 could distinctly see the whole of Mercury's disc, at which time, I judged it about bisected by the sun's

limb.

h

At 3 56 25.905 I judged the limbs of the sun and Mercury accurately tangent. (2d contact.)

m

At 3h 57 15.65 saw what I took to be a line of light between the limbs, but as I afterwards saw what I took to be a very delicate line of light encircling the planet's disc, it may have been this which I saw at this time.

m

At 3h 57 275-77 certainly saw the cusps of sunlight meet around the planet's disc, and,

At 3h 58 06. saw the planet fully upon the sun's disc with as much as 2" space between limbs.

The air was very clear, no clouds being in sight; the only thing in the way of very accurate observations was the disturbance of the sun's limb by puffs of cold air, and they were intermittent.

I saw a copper-red, trapezoidal spot on the planet's disc, and could make out at intervals the encircling line of light before spoken of.

I saw that the planet's disc was not black, but had a grayish hue, it appearing of a lighter gray at the center. The times given are 120th meridian time, taken from the telegraphic signals sent out from the Lick Observatory on the 8th, 9th and 11th instants. Very respectfully,

(See page 242.)

CHAS. W. IRISH, Civil Engineer.

OBSERVATIONS OF THE TRANSIT OF MERCURY, MAY 9, 1891, BY WILLIAM S. MOSES, SAN FRANCISCO.

[Mr. MOSES kindly sent to the Lick Observatory a letter describing his observations together with a drawing of the phenomena showing two phases at ingress and the position of the planet at 5 and 6 P. M. The following abstract gives the necessary data.]

Place of Observation: Masonic Cemetery, San Francisco; the

latitude and longitude are given by Mr. MOSES on the authority of Mr. WM. M. PIERSON, as follows:

Instrument: 71⁄2-inch Reflector made by J. A. BRASHEAR, of Allegheny.

Observer: WILLIAM S. MOSES.

Watch-Correction: One-third second slow, as determined by Mr. F. H. McCONNELL, by comparison with his clock, which is daily compared with the L. O. time signals.

The time-signals require the further correction +0.75 hence the watch-correction was +15.08, which has been applied.

Observations: The sun's image was projected on white paper inside of a dark box so as to be 55% inches in diameter. The first notch in the limb was noted at 3" 54" 298, and the second phase noted was when a ring of light (about one-fifth of the diameter of the planet in the sketch) had been formed, at 3 58 26. These times require the correction above given. Drawings of the various groups of sun-spots are given also. The first contact was well seen; the second phase was not so satisfactorily observed.

OBSERVATIONS OF THE TRANSIT OF MERCURY, MAY 9, 1891, BY WILLIAM M. PIERSON, SAN FRANCISCO, CAL.

I observed the 1st and 2d contacts of Mercury's transit to-day. My observatory is in

Observation made with 81⁄2-inch reflector equatorially mounted. Power used 25.

Clock set to P. S. time obtained from F. H. McCONNELL at 2 P. M. [This requires the further correction of +0.75.]

Observation made on bristol-board screen 18 inches from

eye-piece.

From 3h 50m until after second contact limb of sun very unsteady but at moments definition good.

First contact, limb unsteady, time 3" 54" 225 +0.75.

Until planet half on disc it presented the appearance of paral

lelogram projected at right angles to the sun's limb. time to second contact disc of planet of normal shape.

m

From that

Second contact 3h 57 42+0.75. Limb very unsteady and I suspected that that was cause of second contact occurring apparently earlier than predicted, but within five seconds afterwards the definition was momentarily good and could perceive line of light between planet and limb. Unless this was effect of planet's atmosphere the second contact occurred at the time above given. A fine sun-spot, about 10' from planet at ingress, lent interest to the phenomenon. WM. M. PIERSON.

OBSERVATIONS OF THE TRANSIT OF MERCURY, MAY 10, 1891, BY PROF. T. C. GEORGE, UNIVERSITY OF THE

PACIFIC, COLLEGE PARK.

[From a note by Professor GEORGE, the following data are taken.]

Place of Observation: Observatory of the University of the Pacific, whose latitude and longitude are

Instrument: Six-inch equatorial by ALVAN CLARK, magnifying power, 140 diameters.

Observer: T. C. GEORGE.

Watch-Correction: Derived from L. O. time signals (which require the correction +0.75, which has been applied).

WHO DISCOVERED THE OPTICAL PROPERTY OF LENSES? [NOTES BY DR. J. -L. E. DREYER, DIRECTOR OF THE OBSERVATORY OF ARMAGH, AND BY PROFESSOR SCHIAPARELLI, DIRECTOR OF THE OBSERVATORY OF MILAN.]

[Our members will recollect a question raised by Professor HANKS, and treated at some length in Publications A. S. P., vol. III, No. 15, page 133. It has received a solution in a private letter from Dr. DREYER dated May 15, 1891, lately received at the Lick Observatory, as follows:]

"I read yesterday, with much interest, No. 15 of the Publications A. S. P. I am happy to be able to tell you who HOSTIUS was, though I am afraid you will be disappointed when you become acquainted with him, for he was a most atrocious ruffian! You will find all about him in SENECA'S Quæstiones naturales, lib. I, cap. xvi.

"It is enough to say that he did not use a lens, but merely a mirror specula imagines longe majores reddentia, in quibus digitus bracchii measuram et longitudine et crassitudine excederet.' He lived at the time of AUGUSTUS, and no doubt it was merely a slip that AGRIPPA quoted COELIUS instead of Seneca.”

Professor SCHIAPARELLI writes as follows:

Monsieur le Professeur et honoré Collègue:

MILAN, le 18 Mai 1891.

J'ai reçu votre dernière lettre et je vous suis bien obligé pour les sentiments de bienveillance dont elle est l'expression.

En lisant dans le dernier cahier des Publications of the A. S. of the Pacific l'article "Who discovered the optical properties of lenses"? et la discussion sur HOSTIUS, je me suis rappelé que l'histoire de ce curieux personnage (qu'il ne faut pas confondre avec l'auteur du pöeme De Bello Histrico) est racontée avec assez de details dans l'Ouvrage si intéressant de Senèque, Quaestionum Naturalium libri VIII; cherchez livre I, Chap. 16. HOSTIUS QUADRA vivait du temps d' Auguste et il etait fameux par ses débauches; il obtenait à l'aide de miroirs courbes l'amplification apparente de certains objets. Le passage de Senèque montre qu'a cette époque on connaissait l'effet des miroirs courbes non seulement pour modifier les dimensions apparentes des objets, mais aussi pour en déformer l'image à plaisir. Il n'y est point question de lentille.

Mais il parait qu'une lentille divergente etait employée par NERON (qui etait myope) pour voir mieux les spectacles du cirque; du moins c'est l'interprétation plus naturelle qu'on peut donner à un passage de PLINE, Hist. Nat. XXXVII, 5. Il est bien certain que les anciens connaissaient d'une manière empirique et approximative l'effet des lentilles et des boules de verre sur les dimensions apparentes; ils les employaient comme verres comburants pour concentrer les rayons du soleil et allumer le feu.

Tous les témoignages des anciens Auteurs sur cette matière ont été recueillis et discutés aver beaucoup de compétence dans le