T. B. Harding. — On Occultations and Solar Eclipses. 477 



Art. LIV. — A New and Simple Graphic Method of pro- 

 jecting Occultations and Solar Eclipses not hitherto 

 published. 



By T. B. Harding. 



Communicated by R. C. Harding. 



[Bead before the Wellington Pldlosopliical Society, 6th September, 1893.] 



Plate LIII. 



If any apology be necessary for bringing the following paper 

 before the Society it will be found in the fact that there will 

 be a good occultation of the planet Venus on the evening of 

 the 13th instant. Conjunction of ? with the Moon takes 

 place at Ih. 49m. p.m., New Zealand standard time, and the 

 planet's hour-angle is then 2h. 45m. ; so that, while those 

 bodies are sufficiently high in the heavens for observation, it 

 will be late enough to see them well defined. To proceed : 

 When we consider the abstruse and difficult methods usually 

 employed for the computation of the circumstances of an 

 occultation or solar eclipse for any particular station on 

 the Earth's surface it will be conceded that a ready and easy 

 process of doing this is a desideratum to many who, while 

 they wish to perform. the work, are deterred by the labour of 

 the methods usually employed. In this now proposed, and 

 used by myself for several years, we have such a method, and 

 one in which the mathematical work so much dreaded by the 

 ordinary individual is almost entirely eliminated, and by 

 which any person of only ordinary intelligence and skill in the 

 use of rule and compasses may very readily perform the work. 



For this purpose we require — (1) An ordinary diagonal 

 scale, by which we can get three places of figures ; (2) a 

 sector, or line of chords (which is to be found on any good 

 scale), for measuring and setting off angles ; (3) the " Nautical 

 Almanac " for the year. 



To understand the details of the scheme, we have to sup- 

 pose ourselves, i^ro tempore, at the star's (or sun's) centre, 

 from which we are able to see the Earth and Moon as circular 

 discs, revolving in their orbits, and during an occultation 

 we observe that of the Moon passing between us and the 

 Earth, and covering a certain zone of her disc. We note the 

 parts so hidden from us, and the times at which they are 

 covered and reappear. 



We find all the data for this in the pages of the " Nautical 

 Almanac," where the calculations are made for the Earth's 

 centre ; but from our position we are able to note places on 



