314 Royal Astronomical Society. 



occultatlons, which I have found useful in drawing the attention of 

 some of my pupils to this valuable method of determining meridian 

 distance. 



" The prediction of the time is almost an essential preliminary to 

 the observation, and the computation required for this, in the usual 

 way, is such as to put it altogether beyond the reach of many who 

 would otherwise be perfectly able and willing to make the observa- 

 tion, and who have many valuable opportunities in the course of their 

 profession of improving geography by such means. The method is 

 simply delineating the essential points in the orthographical projec- 

 tion of the moon's motion and that of the observer in a plane per- 

 pendicular to the direction of the star. This is simplified to the ut- 

 most by means of scales, and I find that, with a little practice, my 

 pupils have no diflSiculty in predicting the time of observation to 1 or 

 1-| minute, and this without much care being taken in the drawing. 

 From several occultations, which I predicted and observed here, and 

 from numerous examples taken from the Astronomical Society's 

 Transactions, I find that, with ordinary care, the predicted time may 

 be depended upon within one minute, and that the time occupied in 

 doing so varies from 10 to 15 minutes. As this is sufficiently near 

 for all the wants of the observer, it may, perhaps, serve to supersede 

 tlie method of computation, which, in its simplest form, is an irk- 

 some task, and probably tends to make occultations less frequently 

 observed than they otherwise might be. 



" With officers duly initiated, and observatories at work, observing 

 all that are visible as a regular part of their duty, the most valuable 

 results to geography might be anticipated. 



" I have appended a rule for computing the moon's right ascen- 

 sion and the consequent error of assumed longitude, which is derived 

 from the same method of orthographical projection. It is rigidly 

 correct in princijjle (with the exception of taking small arcs instead 

 of their sines, which in no case affects the result in any sensible 

 degree), and the results of computation may be depended upon 

 within a hundredth part of a second of right ascension if the data 

 are correct, and a considerable error in the estimated longitude, will, 

 I think, be found to have as little injurious eflfect as in any other 

 method of computation." 



'•Bombay, May 1,1844." 



V. Some Remarks on the Great Comet of 1843, as seen in the 

 neighbourhood of Paramatta, New South "Wales. By the Rev. 

 W. B. Clarke. Communicated by Sir John Herschel*. 



The principal point to which the author directed his attention, 

 during the time of the visibility of the comet, was the fact of the 

 existence of a small train of light inclined at a small angle to the 

 large train. 



His own observations were corroborated by those of the Bishop 

 of Australia, who had made distinct notes of its appearance. His 

 lordship says : — 



" On the evenings of Thursday the 2nd instant, and again on 

 Saturday the 4th, my attention was drawn to the remarkable spec- 

 • See ante, p. 308. 



