44(3 HerscheV s Catalogue of Nebulce. 



turn the candlestick on the level board, and observe the 

 afternoon contacts. Apply the ordinary rule for equal altitude 

 observations, and the result will be very near the correct one, 

 even with such an extempore contrivance. The equations to 

 equal altitudes, which are required in the calculation, can, for 

 all ordinary purposes, be reduced in number so as to occupy 

 only a page or two of a pocket-book, entailing only a little 

 extra trouble in working proportions. If the traveller should 

 not happen to have either a levelling board or spirit level, he 

 may roughly supply their places by a thick square of glass (a 

 looking-glass will answer the purpose) and a boy's marble, by 

 which he may adjust it with considerable accuracy. The 

 telescope, in the absence of a clip, can easily be braced to a 

 piece of wood fixed in the candlestick. The candlestick will 

 on many occasions be found to be a most useful telescope- 

 stand, presuming that no better is at hand. This application 

 of it, I believe, originated with Mr. Eonalds, of the Kew 

 Observatory. To the traveller, a substitute for the equatorial, 

 or rather " Smeaton's Block/' may also be of service — he may 

 provide one by fixing his portable telescope by its stand on 

 the lid of a box, and raising the lid by a wedge or stay to the 

 angle required for the latitude of the place. 



[The success of Mr. Heineken's mode of using a telescope 

 will much depend on the comparative temperature of the room 

 in which it stands, and of the air outside. If one part of the 

 telescope tube is much warmer than the other, air currents 

 will be set in motion, and the distinctness of its performance 

 damaged. The nearer to the eye-piece the " taper sleeve " 

 is fixed, the greater the probability of avoiding this source 

 of error. — Ed.] 



HERSCHEL'S CATALOGUE OF NEBULAE. — THE 



ACHROMATIC TELESCOPE.— THE PLANETS OF 



THE MONTH.— OCCULTATIONS. 



BY THE EEV. T. W. WEBB, A.M., F.R.A.S. 



A short notice appeared in our last number of Sir John Her- 

 schel's new General Catalogue of Nebula?. From the notrs 

 appended to that most valuable monument of laborious accu- 

 racy, the following remarks have been compiled, as possessing 

 a considerable degree of interest for every lover of astronomy. 

 Our readers have already been made aware that a strong 

 impression of variability has existed with regard to some of 

 these mysterious objects. This is by no means dissipated by 

 the observations contained in the present catalogue. It is true 



