August i8, 1923] 



NA TURE 



247 



The British Photographic Research Association, 

 '1 which was the first Research Association to be formed 

 under the Department of Scientific and Industrial 

 Research, completed its term of five years in May 

 last. A thorough and searching investigation of the 

 work accomplished has been made by the Depart- 

 ment, which has also taken into consideration the 

 researches which are either in progress or are con- 

 templated, with the result that a further grant in 

 aid for a period of years has been promised. Although 

 the financial position of the photographic industry, 

 which is comparatively a small one, is at present at 

 a very low ebb, it is very satisfactory to note that 

 the leaders of the industry are so convinced of the 

 valuable work done by the Research Association, 

 and of the good results which are likely to accrue, 

 that it has been decided to carry on its operations. 



The Association has had to contend with considerable 

 difficulties during its first five years, but, under the 

 directorship of Dr. Slater Price, it has now a well- 

 established reputation not only in this country, but 

 also in Europe and America. A number of papers 

 dealing with fundamental principles have been 

 authorised for publication in the various scientific 

 journals. 



The Maidstone Museum has set a good example to 

 other provincial institutions of this class by issuing 

 a set of post-cards, published at \\d. each, illustrating 

 its prehistoric collections. These include a clay bowl 

 attributed to the Bronze Age ; palaeoliths of the 

 Chellean period ; a group of eoliths ; some neolithic 

 flint implements — all found in the vicinity. The 

 series also includes a set of good examples of Roman 

 glass. 



Our Astronomical Column. 



D'Arrest's Comet. — MM. Dubiago and Lexin con- 

 tinue the search ephemeris of this comet (for Green- 

 wich Noon) : they use practically the same elements 

 as those deduced by Mr. F. R. Cripps. There is still 

 a prospect of finding the comet, as the greatest surface 

 brightness is not attained until September 12 ; but 

 the object is in considerable south declination in 

 September and October. 



R.A. S. Decl. 

 h. m. 



Sept. 8. 17 43-1 16° 58' 



13- 17 57-9 19 22 



18. 18 13-8 21 34 



The Shower of August Meteors. — Mr. W. F. 

 Denning writes : — " The fine warm weather and 

 absence of strong moonlight enabled these meteors to 

 be well observed during the period from August 3-1 1. 



" The display, however, up to the time of writing 



(August 12) has not been an abundant one, though a 



fair number of Perseids appeared each night, and the 



radiant showed its usual displacement to the east- 



i north-east. 



" Mr. J. P. M. Prentice, at Stowmarket, recorded 

 the flights of 250 meteors up to August 9, and had 

 recognised a number of the usual minor showers, 

 including a Capricornids, 5 and 7 Aquarids, 5 Cassio- 

 peids, 7 and Q Cygnids, Sagittids, e Taurids, a - /3 

 r Perseids, {i Piscids, and Lacertids. Mr. Prentice saw 

 ^ a splendid Perseid fireball on August 9, i2h. 32m. 

 G.M.T., with an estimated magnitude greater than 

 that of the full moon. The streak lasted 23 seconds, 

 and its colour was bright blue surrounded by bright 

 red. 



" Mr. A. King watched the shower from Lincoln- 

 shire on and after August 3, and saw a fair number of 

 Perseids. At Bristol some observations were made 

 on August 4-11, during which period the Perseids 

 were only moderately active. The brightest meteor 

 seen at Bristol was a Cygnid on August 11, g.40 

 G.M.T. It was brighter than Jupiter, and traversed 

 a short path from 289° +66° to 289° +72° ; it left a 

 white streak for a second, across 5 Draconis." 



Prof. R. Schorr's " Eigenbewegungs-Lexicon." 

 — Prof. Schorr, director of Bergedorf Observatory, 

 Hamburg, has just brought out a very useful work 

 of reference in the form of a comprehensive catalogue 

 of practically all the known proper-motions of stars. 

 It is arranged in zones of declination, 1° wide, the 

 designation of the stars being taken from the Durch- 

 musterungs of Bonn, Cordoba, and the Cape. It is 

 numbered by columns (two to a page) and there 

 are 400 columns, each containing some fifty stars. 



NO. 2807, VOL. I 12] 



Only one determination is given of each motion, 

 presumably the best available ; the authorities are 

 given in each case. The centennial motion is given 

 to two decimals of a second of time in right ascension, 

 and one decimal of a second of arc in declination; 

 a few stars are given to one figure less than this. 



To diminish cost the work was typewritten, and 

 then multiplied by a mechanical process, the result 

 being perfectly clear and legible. The price is fixed 

 at thirty Swiss francs. 



Already a first supplement has appeared, con- 

 taining 1739 stars ; some of these, marked " !," are 

 improved values for stars already in the Lexicon, 

 but the majority are additional stars. 



This is the second very useful work that Prof. 

 Schorr has issued in a few months, his new reduction 

 of Riimker's Hamburg Catalogue having lately 

 appeared (Nature, April 28, p. 564). 



The Free Pendulum. — Mr. F. Hope- Jones de- 

 livered a lecture on this subject to the British 

 Horological Institute on April 19, and it has lately 

 been issued as a pamphlet. He lays stress on giving 

 the pendulum that we rely on as primary time-keeper 

 as little work to do as possible ; his three desiderata 

 are : (i) the maintaining impulse must be given at 

 the zero (lowest) position ; (2) it must only be given 

 occasionally ; and (3) there must be no other inter- 

 ference with the pendulum. 



Mr. Hope-Jones states that this problem has been 

 solved, quite independently, by five men in the last 

 twenty-five years : Mr. Rudd in 1898, Sir David 

 Gill in 1904, Mr. Bartrum in 1913, Father O'Leary, 

 S.J., during the War, and Mr. W. H. Shortt, who 

 has been at work since 1911 on the matter, his clock 

 being installed at Edinburgh Observatory early in 

 1922. The details of each of the five methods are 

 briefly given, but the last is considered much the 

 best. The fundamental pendulum, constructed of 

 invar, is in an air-tight case, pressure 3*5 cm., kept 

 at constant temperature. It receives its impulse 

 every half - minute, at the lowest position ; the 

 remontoire is worked by the slave-clock, which is 

 synchronised by a " hit or miss " action to within 

 001 second. Two diagrams of the changes of weekly 

 rate in periods of three months are given ; the range 

 of weekly rate is 0-02 second per week. Prof. 

 Sampson notes that the clock is superior to the Riefler 

 instrument, though that is a very fine clock. 



A clock with uniform rate is of great importance 

 in fundamental astronomy for the removal of the small 

 systematic errors in right ascension ; they have 

 been greatly reduced, but not wholly removed. 



