December 23, 1909] 



NATURE 



227 



port were expressed in general terms so as to admit of 

 modifications in details at the various national standard- 

 ising laboratories. The appendix now issued contains 

 details of the methods adopted at the National Bureau of 

 Standards of America, at the Central Electrical Laboratory 

 of Paris, at the Reichsanstalt at Berlin, and at the National 

 Physical Laboratory at Teddington. References to the 

 literature of the subject are also given, so that this 

 appendix will prove of great use in electrical laboratories. 



The Naturwissenschaflliche Wochenschrift, the organ of 

 the German Society for Popular Science of Berlin, devotes 

 almost the whole of its issue of December 4 to the first 

 of a series of three articles on the experimental founda- 

 tions of the atomic theory, by Mr. Werner Mecklenburg. 

 After a short historical introduction the author deals with 

 the evidence for the existence of discrete particles in optic- 

 ally clear colloidal solutions, and then goes on to the 

 kinetic theory of gases as one of the means of determining 

 the size of the actual molecule of matter. Under this 

 head simple proofs of Boyle's law, of the relation between 

 mean free path and viscosity, of Van der Waals's equation, 

 and of Loschmidt's method of calculating the radius of a 

 molecule are giwen. As the method of treatment of the 

 subject is not unlike that adopted in Meyer's kinetic theory 

 of gases, readers of the above weekly must be interested in 

 science to a greater extent than the public generally gets 

 credit for being. 



Messrs. Burroughs, Wellcome and Co., of Snow Hill 

 Buildings, E.G., have issued their exposure record and 

 diary for 1910. This pocket-book is so well known among 

 photographers that the chief object of this note is to 

 inform them that the 1910 issue is now ready. It is 

 important to point out that three editions are issued and 

 bound in different tints, according as they are especially 

 arranged for the northern or southern hemisphere or for 

 the United States of America. The pocket-book itself is 

 a mine of practical information set up, so to speak, in 

 tabloid form, and the concentrated essence of the contents 

 together with the pages for entering exposure records and 

 for a whole diary, is all enclosed in a very neatly got-up 

 covering which will stand constant wear and tear. It 

 must not be forgotten that a very important feature is 

 the mechanical exposure calculator, practically the simplest 

 efficient instrument, which is fastened inside the back 

 cover. One turn of one scale tells the correct exposure 

 for any subject, at any time of the day or year, in any 

 part of the world. The writer of this note has used one 

 of these books for several years, and finds, to his regret, 

 that to be without his copy means a great uncertainty in 

 giving correct exposures. Issued at a price of one shilling, 

 it is an extremely good investment. 



A NEW apparatus has recently been installed in the 

 mechanical engineering department of the Northampton 

 Institute for testing aeroplane models, and is described in 

 an article, by Messrs. C. E. Larard and R. O. Boswall, in 

 Engineering for December 10. The apparatus consists 

 essentially of a carriage supported on four wheels running 

 on a long straight track, and carrying the model aeroplane. 

 The carriage is drawn along with increasing velocity by 

 means of a horizontal cord, which is attached to the 

 carriage at one end and to a large drum at the other end. 

 The drum is rotated by falling weights, and the velocity 

 of the carriage at any instant is obtained from a record 

 traced on a moving strip of paper by a vibrator making 

 five complete vibrations per second. When a sufficient 

 velocity has been attained the model lifts, i.e. flight begins, 

 and the instant at which this occurs is marked on the 

 NO. 2095, VOL. 82] 



strip of paper electrically. The velocity at which flight 

 begins can thus be determined easily. The authors prefer 

 this form of apparatus to the whirling-table method, and 

 hope to make a series of tests on planes of varying shapes 

 and dimensions. Experiments are now being made to 

 determine the velocities at different angles, and also to 

 show the manner in which the centre of pressure alters 

 as the angle of the plane is varied. It is also proposed 

 to instal a considerably larger apparatus than the exist- 

 ing one, which has a track 60 feet long at present. 



The twenty-sixth annual issue of the " Year-book of the 

 Scientific and Learned Societies of Great Britain and 

 Ireland " has been published by Messrs. Charles Griffin 

 and Co., Ltd. The book has been compiled from official 

 sources, and is intended to be a record of the work done 

 in science, literature, and art during the session 1908-9 

 by numerous societies and Government institutions. In 

 some cases the lists of papers read before societies are a 

 little belated. For instance, it should have been possible 

 in December, 1909, to publish the titles of papers read at 

 the Winnipeg meeting of the British Association last 

 summer in the place of those read in Dublin in 1908. 

 Exhaustive though the list of societies is, it is not yet 

 complete. Certain local geographical societies are dealt 

 with, but the Geographical Association, with its numerous 

 branches, receives no mention — an omission we have 

 pointed out on a previous occasion. 



OUR ASTRONOMICAL COLUMN. 



Daniel's Comet, 19096. — Dr. Ebell's ephemeris for 



Daniel's comet, igoge, is extended to January 2, 1910, in 



No. 4376 of the Astronomische Nachrichten (p. 127, 



December 14), and the following is an extract therefrom : — 



Ephemeris I2h. M.T. Berlin. 



a(lrue) {(true) Bright- 



1909 h. m. , , log r log .i ness 



Dec. 21 ... 6 190 ... +45 347 ... o-20og ... 08022 ... o-gz 

 ,, 25 ... 6 19-2 ... +4S 158 ... 0-2032 ... 0-8128 ... 0-87 

 ,, 29 ... 6 19-4 ... 150 40-7 ... 0-2059 ... 0-8253 ... 0-81 



rgio 

 Jan. 2... 6 19-6... -1-52 478 ... 0-2092 ... 0-8404 ... 074, 



The elements given by Dr. Ebell show a likeness to 

 those calculated by Dr. Becker for comet 1867 I. (Stephan), 

 which are given for comparison ; the " period " given in 

 the latter is 40-1 +20 years. A number of observations 

 are recorded in the same journal. On December 8 the 

 comet was easily seen in the 8-cm. (3-2 inches) finder at 

 the Uccle Observatory, and appeared to be of about magni- 

 tude 95 ; a nucleus of the twelfth magnitude and about 

 12" in diameter was seen to be surrounded by a coma 

 which was 3' in diameter. Observers at Algiers and 

 Arcetri on December 9 estimated the magnitude at 10-5 

 and 11-5 respectively. 



Halley's Comet. — Visual observations of Halley's 

 comet with small instruments are now becoming common, 

 and a number are recorded in No. 4376 of the Astrono- 

 mische Nachrichten. Prof. Nijland reports that the comet 

 was certainly visible in a 73-mm. finder on December 5, 

 its magnitude being estimated as no. Herr v. Buttlar, 

 using a 3|-inch telescope on December 4, saw the comet 

 as a nebulous mass of about 45" diameter, having a magni- 

 tude of about 11-5. 



Subjective Phenomena on Mars. — In No. 4358 of the 

 Astronomische Nachrichten M. Antoniadi suggested, be- 

 cause it is not shown on photographs, that the dark band 

 which surrounds the disappearing polar cap on Mars is 

 probably a subjective phenomenon. In a later number 

 (4363) of the same journal M. Jonckheere contested the 

 subjectivity of a band which was irregular in form and 

 might be obliterated from the photographs by the 

 photographic " spreading " of the image of the brilliant 

 polar cap. 



To these suggestions M. -Antoniadi replies, in No. 4376,- 



