ASTRONOMY. 303 



Paramatta, IS". S. W., which oiijiinally appeared in Brewster's Edinburgh 

 Journal of iScience^ 1827, and which have been a good deal overlooked, 

 that periodical, on the Continent at least, not being easy of access. 

 Dunlop's drawings are reproduced, and there are several figures of the 

 two bright comers of 1881. Wiih regard to his investigations generally, 

 Professor Bredichin concludes: 



" My researches on all the comets of which I have been able to find 

 observations in astronomical literature (30 comets), place me now in a 

 condition to jcalculate in advance, for each great comet that appears, 

 the positions and the figure of its tails of all three types. It is evident 

 that the relative amount of matter in tails of ditierent types cannot be 

 determined in advance, and, consequently, observation alone can show 

 us the relative brightness of the types and the possible absence of one 

 or another of them. But, in every case, the positions and the general 

 form of such of the tails as become visible will be in accord with the 

 l^ositions and figure calculated beforehand." 



PLANETS. 



Vulcan. — In the report of the director of the Washburn Observatory 

 for 1882, is given an account of experiments with the Watson Solar 

 Observatory. Thi.^ we give in full, as it probably will not be published 

 elsewhere, and on account of the general interest in the success of this 

 experiment. 



The solar observatory was devised for the purpose of seeing a planet 

 or stars in the daytime. 



It consists essentially of a covered cellar large enough to contain an 

 observer and a six-inch telescope. From the north wall of this cellar 

 a tube 12 inches in diameter and 55 feet long is directed to the north 

 pole. At the upper (north) end of this tube a heliostat, or mirror 

 driven by clock-work, is to be placed. The idea is that the images of 

 stars will be reflected down the tube by the mirror and seen by an ob- 

 server in the cellar througli the telescope. When I took charge of this 

 observatory the building was entirely incomplete, and no instruments 

 were available for trying the experiment. I have borrowed from Profes- 

 sor Langley, director of the Allegheny Observatory, a heliostat suitable 

 for the purpose, and the regents of the university have bought from 

 Mr. Burnham, of Chicago, his six-inch Clark telescope; and the build- 

 ing has been completed. Six weeks have been spent in thoroughly try- 

 ing the experiment. The trial is now concluded, and the result is that 

 the solar observatory is not suitable for showing stars as faint as the 

 third magnitude in the daytime, even when they are distant from the sun. 



Therefore there is no use in proceeding further with this means in 

 the search for Vulcan, which was estimated by Professor Watson to be of 

 the four-and-a-half magnitude, and which, from the nature of the case, 

 must always be near the sun. The details of the experiment are given 

 in the following extract from the annual report : 



