168 ASTRONOMY FOR 1889, 1890. 



lisli and the French forms. The pillar that supports the polar axis Is 

 not upright, but L-shaped, the lower part being inclined nearly in the 

 plane of the equator, the upper almost at riglit angles to this, extend- 

 ing toward the north pole and inclosing the polar axis. The support 

 possesses very great stability, and its form permits an uninterrupted 

 motion of the telescope in all i>ositions. 



In Engineering for December 19, 1890, will be found a description of 

 the Melbourne photographic telescope made by Sir Howard Grubb. 



An instrument for comparing and measuring celestial photographs, 

 somewhat similar to that designed by Mr. Eoberts, has been devised by 

 Mr. Common. 



An apparatus for eliminating personal equation in the observation of 

 sudden phenomena, such as the disappearance of a star when occulted 

 by the moon has been devised by Mr. S. P. Langley, and is described 

 in the Bulletin of the Philosoi)hical Society of Washington, vol. xi. 

 The principle of the method consists in associating a motion, real or 

 apparent, of the object, with intervals of time so that the apparent posi- 

 tion of the object at the instant of the occurrence of any phenomenon 

 being noted the time of the occurrence will be known. Experiments 

 made with artificial stars show that it is quite possible for a compar- 

 atively inexperienced person to observe an occultation with a probable 

 error of only one-fortieth of a second. 



The great Lick refractor of 36 inches diameter is to be surpassed by 

 one still larger, ordered for the University of Southern California, at 

 Los Angeles. This lens is to be 40 inches in diameter, and the crown 

 glass disk for the achromatic combination is now in the hands of the 

 Clarks, who pronounce it a remarkably fine piece of glass. 



It may perhaps be mentioned here that a bill was introduced in the 

 United States Congress making an appropriation of $1,000,000 for a 

 refractor of 5 feet aperture for the U. S. Naval Observatory, but the 

 X^lan never received support from the Government astronomers. 



Mr. Brashear has under way at his shop in Allegheny a 16 inch 

 objective for Carleton College Observatory, one of 12 inches for Brown 

 University, and a second of 12 inches for Mr. G. E. Hale, of Chicago. 

 He is also making a large spectroscope and spectrograph for Professor 

 Young, at Princeton, which is expected to be the finest in the United 

 States; a very complete spectroscope with Jena glass objectives and 

 prism is being made for Carleton College, and a new star spectroscope 

 for Lick Observatory. Eor the Willard photographic telescope of the 

 Lick Observatory, he is making an equatorial mounting with controlled 

 clock. 



MISCELLANEOUS, 



Personal equation. — The attention of astronomers interested in the 

 subject of personal equation should be directed to a paper prepared 

 by a physiologist, Dr. E. C. Sanford, of the Johns Hopkins University, 



