404 



NATURE 



[StPTEMF.ER 29, 1 910 



in which (a) one parameter has a value slightly below 

 2-780, or (!i) two of the parameters are nearly equal. 

 Amongst the sulphonic chlorides and bromides two iso- 

 morphous series are seen, the second series being restricted 

 to compounds in which an iodine atom is present ; it is 

 noteworthy that the two chloriodobenzenesulphoiiic 

 chlorides are found in different series, and that one of 

 them was on one occasion obtained in a labile form, the 

 crystals becoming cloudy and opaque when removed from 

 the solvent from which they had separated. This 

 behaviour indicates clearly that certain members of the 

 series are actually dimorphous, and the whole series may 

 therefore be regarded as isodimorphous. Isodimorphism 

 was also detected amongst the anilides and toluides. It 

 is remarkable that two other series, containing the halogen 

 atoms in the meta position, which were examined by Dr. 

 E. C. Jee in 1900, proved to be isotrimorphous and iso- 

 letramorphous respectively. The completion of the work 

 on these series will be awaited with interest. 



A SECOND edition of "A Text-book of Zoology," by 

 Profs. T. Jeffrey Parker and W. A. Haswell, is announced 

 as nearly ready by Messrs. Macmillan and Co., Ltd. The 

 work has been subjected to careful revision throughout ; 

 some parts have been to a great extent rewritten, and a 

 considerable number of new illustrations have been added. 



OVR ASTRONOMICAL COLUMN. 



\'elocities and Acceler.ations of the Ejecta from 

 Hallev's Comet. — Profs. Barnard and Lowell and Senor 

 J. Comas Sola all deal with the velocities and accelera- 

 tions of the matter ejected from the body of Halley's 

 comet, during May and June, in No. 4441 of the Astro- 

 Homische Nachrichlen (pp. 11-16). 



From measures of photographs taken at the Yerkes 

 Observatory (Y), Honolulu (H), and Beirut (B) on 

 June (1, Prof. Barnard found the velocities of recession, of 

 a well-marked feature in the tail, given in the following 

 table : — 



Interval jj„„^, Recession per second 



Stations between motion '' ^ 



iihotographs From comet From sun 



Hours , Miles km.' Miles km. 



Y-H ... 4-25 ... 360 ... 23-1 ... 37-2 ... 397 ••• 63-9 



Y-B ... 15-15 ... 5-17 ... 33'i ■•■ 533 ■•• 497 ••■ So-o 



H-B ... 1090 ... 578 ... 373 • ■ 597 •■• 539 ••■ 864 



These results show a strong acceleration in the mass 

 measured, which was about i-s" from the head; from 

 the last two photographs this acceleration was about 

 14 miles (22 km.) per second. 



Similar results are obtained by Prof. LoAvell from the 

 measures of two photographs taken, with rather less than 

 an hour's interval, on May 23. On these photographs 

 are shown four knots in the tail, at distances varying 

 from 1° 28' to 6° 15' from the head, and the measures 

 give for the velocities of the particles composing the 

 knots 13-6, 17-2, 19.7, and 29-7 miles per second respec- 

 tively, thus showing an acceleration of the velocities as 

 the particles receded further from the head. 



Senor Sola, dealing with the velocities of the gaseous 

 globes ejected from the nucleus on June 4, shown on 

 photographs taken on June 4, 6, and 7, finds that between 

 June 4 and 6 the acceleration of these ejecta was 0-148 

 metre per second, and between June 6 and 7 was 

 C1248 metre per second. 



Observations of Comets. — New observations of three 

 comets are published in No. 4441 of the Astronomische 

 \achrichteii. A number of observers give positions, deter- 

 mined during August, of Metcalf's comet, 1910b, and 

 generally describe it as a faint object, magnitude about 

 no, having a central condensation and a suspicion of a 

 tail. 



D '.Arrest's comet was observed at the Algiers Observa- 

 tory on August 26 and 29 and September i by M. 

 Gonnessiat. The correction to Leveau's ephemeris was 



NO. 2135, VOL. 84] 



an increasing quantity, and on September i had the value 

 — im. 19.39s., -t-6' 16-2"; the comet is described as a 

 diffuse nebulosity of 2' or 3' diameter, with a feeble, 

 central condensation of about magnitude 14.5. 



With a 9-inch refractor Mr. Innes found that, on 

 August II and 12, Halley's comet was a most difficult 

 object, and w'as, therefore, much fainter than the magni- 

 tude (7-4) given in No. 4423 of the Astronomische Nach- 

 richten. Observations made between July 26 and 

 August n indicate a correction of about —lis. to the 

 ephemeris given in the same place ; the ephemeris is 

 nearly correct in 5. When last seen the comet was a 

 nebulous object, of 1' diameter, showing a slight con- 

 densation. 



The Solar Physics Observatory, South Kensington. 

 — From the report published by the Board of Education, 

 dealing with the work done at the Solar Physics Observa- 

 tory, South Kensington, during 1909, we learn that 

 spectroheliograms of the solar disc were obtained on 147 

 days during the year; of the 286 negatives secured, 231 

 have been selected for the measurement of flocculic areas 

 in pursuance of the scheme for establishing a cooperative 

 daily record of such areas. Fifty-seven photographs show- 

 ing the calcium prominences at the limb were also secured 

 with the spectroheliograph. Visual observations of the 

 sun were possible on 232 days, and " no spots " was re- 

 corded on five occasions. The spectra of 138 spots were 

 observed visually, and show that the lines chiefly affected, 

 in the region F-D, are due to V, Ti, Sc, and Mg, 

 associated with H. A powerful instrument for the photo- 

 graphic recording of sun-spot spectra cannot be used 

 owing to the vibration occasioned by traffic in the 

 vicinity. Work with the 36-inch reflector on Halley's 

 comet and other objects w^as also restricted by the poor 

 observing conditions. A large number of photographs of 

 stellar spectra were secured with various prismatic 

 cameras, those obtained with a calcite-quartz optical 

 system being employed for the temperature-comparisons of 

 various stars. 



The Determination of Longitude. — In an interesting 

 brochure of sixty-two pages, now published as an extract 

 from the journal L'Horloger, Dr. Jean Mascart recounts 

 the history of the determination of longitudes, with a 

 special chapter on the invention and development of 

 marine chronometers, and an account of the voyage of 

 the Flore, which had for its purpose the actual testing 

 of the different methods of determination, in 1771-2. The 

 brochure is well illustrated with portraits and cuts of 

 historical instruments and their parts, and contains 

 numerous references to the literature of the subject with 

 which it deals. 



THE ROYAL COMMISSION ON WELSH 



MONUMENTS. 

 "T^HE first report of the commission contains a general 

 ■'■ account of work already done, and an outline of the 

 work proposed to be done. The first volume of classified 

 information the commission hopes to publish in the course 

 of the present year, in the form of an inventory of monu- 

 ments in the county of Montgomery. 



The task undertaken is truly immense. No type of 

 monument nor available source of information seems to 

 have been overlooked in the outline given. There are, of 

 course, inevitable limitations to be considered, but it is 

 not likely that the work in value and extent will ever be 

 a subject for serious adverse criticism. .\s, however, the 

 commission's plan of campaign has been published at a 

 time when that plan may be reconsidered in some details 

 before the information collected has been cast into a final 

 form, one may venture to direct attention to a class of 

 facts which is not even mentioned in the report, but which 

 may be shown to be by far the most important within the 

 scope of the inquiry. 



The most important documents are the monuments 

 Ihemselves. Whatever facts may be directly elicited from 

 them take precedence of all facts elicited from " finds," 

 folklore, and documentary information. They may be 



