December, 1910. 



KNOWLEDGE. 



477 



in an observatory, and he may be twenty-three before he gets 

 his degree), but turns out, after appointment upon book work 

 examination, to be an inefficient assistant. A good practical 

 experience in astronomy is not to be gained in a year or two. 



If, on the other hand, one begins observatory' work some 

 years before twenty years of age, he will stand no chance in 

 such examinations. ha\ing for years gi\en the best of his time 

 and energy to practical work to the greater advantage of the 

 observatory and astronomy. If such an one throws himself 

 thoroughly into the practical work of observations and 

 reductions year after year, becomes an expert practical 

 astronomer, and is encouraged in distinct lines of work — as he 

 may seem specially adapted — or to work in a communistic 

 sense, he will find himself debarred, by the age limit, from 

 having any chance of attaining one of the few astronomical 

 assistantships that are so seldom \acant, and will soon be 

 subjected to the irritation of ha\ing to teach a novice and a 

 '■ senior in position " how to do work in an obser\atory. 



Though I am not writing this useless letter for myself, 

 ha\ing gone a very long way past this maximum limit, and 

 well on my wa\- to the three-score and ten limit, I have in 

 my mind several men who have already had 7-20 years 

 thorough experience in practical work and calculations in 



observatories, have contributed papers to the astronomical 

 world, and have universitj- degrees, who, because they have 

 spent so main- years in astronomy, are for ever prevented from 

 rising to higher places as rewards for their past services, by 

 reason of such senseless age Umits and curtailment of the 

 powers of directors of obsersatories in appointing those w-ho 

 they know will best assist the work required to be carried oUi 



C3f course this age limit will continue and noxices be 

 appointed, and appro\ed assistants will be discouraged and 

 set aside so long as directors of observatories are apathetic 

 on behalf of young workers. .Astronomical appointments 

 made on mere written examinations are like marriages ; nmch 

 better appoint a man who could show ten to twenty years 

 work : one examination or a single piece of work will not 

 make an astronomer. 



Those who bear the brunt of astronomical observations in 

 an observatory should be well and better paid, and should be 

 encouraged to improve their knowledge and work by the 

 prospect of rewards to higher positions ; because this class of 

 work is very exacting upon the observer's \igour, energy, and 

 health, and he ought not to be discouraged bj' others of small 

 astronomical experience being appointed over him. 



F. A. BELLAMY. 



g L" ERIE S .A X D A X S W E RS. 



Readers are invited to send in Questions and to ans'ii.er the Queries -^•hicli are printed on tliis page. 



OLE ST IONS. 



Numbers 14. 16. 17. 18 and 20 (page 4611 still remain 

 unanswered- 



REPLIES. 



11. A BOOK OX WASPS.— I can strongly recommend J. G. 

 Sandeman to get Dr. E. L. Ormerod's " British Social Wasps," 

 published about 1S6S, by Longmans, Green & Co.. at 10 6. 

 and probably now out of print, but to be obtained second- 

 hand for a few shillings. It deals with the life-history, 

 anatomy and physiology- of our se\-en British species, gives a 

 short bibliography, and contains illustrations of nests and 

 coloured plates of the species, showing all the sexes. On the 

 whole. I do not think anyone interested in the subject can do 

 better than get a copy of this work, as it is both popular and 



scientific. ^ ,, 



C. Nicholson. 



[We are indebted to Mr. E. E. Banham for kindly recom- 

 mending and letting us see a copy of this same book. — Eds.j 



13. THE FINDING OF TIME AT NIGHT.— It is to 

 be presumed the stars are shining and that the Observer 

 knows the Pole Star and its Pointers. Stand facing towards 

 the Pole Star and imagine a great clock face about 35 radius 

 figured on the heavens re\-ol\ing round the Pole Star in a 

 direction opposite to that of an ordinary clock hand. This 

 imaginary clock face has twenty-four hours marked in the 

 usual order round the face in such a way that the Pointers 

 are at XI. 



Suppose it to be in the position in which is overhead and 

 XII verticalh- beneath the Pole Star. 



Now picture to yourself the date of end of Ist week in each 

 month blazoned on the sky permanently fixed. Following the 

 direction of the stars motion. January 7th is at XVI o'clock. 

 February 7th at XII. March 7th at XII. and so on all round. 

 The mental picture of these dates must be fixed. It will be 

 seen we get at the four quarters starting from the bottom. 

 March 7th. June 7th. September 7th. December 7th. We 

 have now only to fix the position in the sky of the date of 

 observation and then reckon round the number of hours to 

 the present position of the pointers. This will give the 

 approximate time. 



The reason is very simple. The date position in the sky 

 is the approximate position the pointers occupied that 

 day at noon ; their present position shews on our imaginary 

 clock face how many hours have elapsed since then. 



Of course the process would be facilitated if so simple an 

 instrument be permitted as a card disc with the dates marked. 

 The card would be held with September 7th at top and at 

 such a distance from the eye that the pointers lie just outside 

 the disc while the Pole Star is seen through a central hole. 

 The disc might be 10-in. in diameter and be held 11 -in. from 

 the eye. 



Hold it with finger and thumb on the date place, keeping 

 Septeniber 7th at top and Pole Star in centre, di-aw it towards 

 your eye till the pointers meet the ed^e. run your free finger 

 and thumb round to their point and read off distances between 

 your thumbs. If a disc is made the correct dates should be 

 taken from \\"hitaker"s .Almanack each month, the Sun Column 

 Sidereal Time at noon, when the hours of Right Ascension or 

 Sidereal Time are completed. It will be easy to see why they 

 must be placed as directed, to give the noon positions of 

 R..-\. XI, which is approximately that of the Pointers. The 

 7th of each month is nearh- right, except for Januarv and 



^^^™'"">-- ' S. E. Percival. 



P.S. — Since sending my reply to Query 13, "Knowledge " 

 for November. I leaxn from Mr. HoUis, seeiJ;/g7(s/( Median ic. 

 November 18th. p. 362. that the plan I suggested was used 

 many years ago in an instrument called a "" Nocturnal," and 

 that it is described in Hatton's Dictionary of Mathematics. 

 1 795. I need hardly say I was (luite unaware of this. 



13. We can arrive at a \-ery rough idea of the time, under 

 the conditions specified in this question (p. 2SS), in the follow- 

 ing manner, which will necessitate the visibility of moon and 

 stars. To simplify demonstration, suppose the moon is full, 

 then the shadow of a perpendicular object will indicate the 

 direction of the celestial sphere in which the sun is situated, 

 and from a knowledge of the position of the Pole Star, this 

 direction can be expressed in terms of the cardinal points. 

 But for rough calculations we may assume that the sun will 

 be due west at 6 p.m.. due north at midnight, and due east at 

 6 a.m. : intermediate positions being deduced on the basis that 

 the sun describes (apparently) 15 degrees every hour. Thus, 

 having found the positii^n of the sun by the abo\-e method, we 

 can ascertain the time. If the moon be not full, a simple 

 calculation depending on the magnitude of its phase will 

 determine the position of the sun. The inadequacy of this 

 method is of course evident, and, furthermore, if w-e assume 

 that the stipulated approximation connotes any reasonable 



