Amriist 30, 1877] 



NATURE 



371 



The Committee forwarded copies of their last year's report to the 

 Admiralty, the Baard of Trade, the Trinity House, and other 

 corporations, but no intimation had been received as to any 

 action being taken upon it. The report was discussed at the 

 conference of the Association for the Reform and Codification 

 of the Law of Nations last year at Bremen, where a resolution 

 was agreed to declaring that the existing international rules for 

 preventing collisions at sea were not satisfactory, and it was 

 desirable the governments of maritime states should take coun- 

 sel together with a view to amenil the rules and adapt them more 

 carefully to the novel exigencies of steam navigation. This 

 showed that the subject had already attracted considerable atten- 

 tion, and it was important to notice that the conclusions of the 

 Committee had not yet in the smallest degree been controverted. 

 Numerous collisions had happened during the year, which, to 

 judge from the law reports, might in many instances have been 

 avoided had the effect of reversing the screw been known and 

 acted upon ; but it did not appear as if a consideration of this 

 had intluenced any of the judgments given. The collisions had 

 for the most part been with small ships, and so had not came 

 much into notice. The loss of the Dakota, however, was a dis- 

 aster of the first magnitude, and would unquestionably cause the 

 subject to be considered by the authorities. 



Report of the Committee for commencing Secular Exferimenls 

 on the Elasticity of Wires. — The Committee have been chiefly 

 occupied with preliminary arrangements and preliminary experi- 

 ments. 



A room has been fixed upon in the tower of the University 

 buildings in Glasgow for suspending wires for the secular experi- 

 ments. In this room there is an available height of sixty feet. 

 A tube of cast-iron, within which the wires are to be hung, is at 

 present being erected, and will be ready in two or three weeks. 

 The tube is to be 60 feet high and 9 x 44 inches in cross 

 section. 



Wires of gold, platinum, and palladium have been supplied 

 by Messrs. Johnson and Mathey, and with these it is proposed 

 to commence the secular experiments. These wires have been 

 specially drawn for the Committee. Each of them weighs one 

 grain per foot. 



A cathetometer suitable for making observations on the wires 

 alter they are hung up in their place has been designed and is 

 being constructed by Mr. James White, instrument-maker, 

 Glasgow. Preliminary experiments have been undertaken for 

 the purpose of determining Young's modulus, and the breaking 

 weight of the gold, platinum, and palladium wires. 



Some experiments have also been undertaken in connection 

 with the subject under investigation as to the effect of continued 

 application of force on the breaking-weight of steel wire and 

 solt iron wire, and results of importance have been obtained. 

 These experiments are still being carried on, and numerical 

 results will be given in a future report. It is found that when a 

 weight nearly as great as the breaking-weight is kept for a long 

 time — several days, for instance — and applied to pull out a soft 

 iron wire, the effect is to increase largely the strength of the 

 wire. It is often increased by as much as 6 or 7 per cent. 



Report of the Committee on Luminous Meteors, by J. Glaisher. 

 — The Committee have to record a year of very active research 

 and of diligent and successful observations of shooting stars, 

 fire-balls, and aerolites since the last report. The toilsome work 

 of mapping and projecting star showers, and comparing and 

 arranging the radiant point in lists, has occupied so much 

 attention that they have been obliged to postpone till next year 

 the work of furnishing observers with a resume of the known 

 star showers. The autumn and winter months were marked by 

 numerous large fire-balls observed in England and abroad, some 

 of which are of very special interest. Two, if not more, 

 aerolites have fallen in America, and one at Constantine, in 

 Algeria. Besides the magnificent meteor seen in the United 

 States on December 21 last, from which one of these aerolites 

 was projected, an equally splendid aerolite passed over Cape 

 Colony on March 16 last with loud explosions, but no aerolites 

 are known to have fallen from it in its flight. Much of the 

 attention of the Committee has been engaged in the continued 

 examination and comparison of star showers, and valuable 

 work has been performed by Mr. W. F. Denning. There have 

 been no marked star showers for one or two years, but some 

 examples of frequency on certain nights have occurred. The 

 August shower of 1876 and of the present month have both 

 been below the average. The work of the Committee has, 



as in former years, been chiefly performed by Prof. A. S. 

 Ilerschel. 



7 he Report of the Committee appoin/eJ to consider the Ordnance 

 Datum Lezel. — l\.{iex detailing the various causes which they found 

 had led to the micertainties referred to in the communications made 

 in 1875, the Committee came to the following conclusions :— ist. 

 That of the two tide gauges at Liverpool, now purporting to 

 refer to the old dock sill, the zero of that fixed at the south-east 

 corner of the Canning dock was about 5 64 inches above that on 

 the river face of the Canning Island, Liverpool. 2nd. That in 

 order to reconcile the statement in the ordnance book of levelling, 

 " that the datum level for Great Britain is S-ioths ofan inch above 

 the mean tidal level obtained from the records of the self-record- 

 ing tide-gauge on the St. George's Pier, Liverpool," with the usual 

 facts which the Committee have collected, it is necessary to bear 

 in mind that the records of the self-acting gauge referred to were 

 the observations of one month only of the year 1S59, and that 

 the mean tide of that period was 7 '8 inches below the mean 

 decade from 1S64 to 1873. 3rd. That the difference of levels 

 between the old dock sill and the ordnance datum, given in the 

 ordnance book of levelling as4'67 feet, is correct on the assump- 

 tion that the zero of the gauge on the face of the Canning Island, 

 and not that of the gauge in the Canning dock, be taken as the 

 correct level of the old dock sill, and that, as slated in the ord- 

 nance book of levelling, the ordnance datum betaken at S-ioths 

 of an inch above the mean tide level of the month of March, 

 1S44, as ascertained by the ordnance department. 4th. That it is 

 thus apparent that the ordnance is an entirely arbitrary level, and 

 could not be again obtained from tidal observations. The com- 

 mittee had thought it advisable to take advantage of the present 

 inquiry in order toobtiin information as to some of the various 

 local datum marks in use in the British Isles, and to endeavour 

 to ascertain the difference of each relatively to the ordnance 

 datum, which would thus be the means of comparison between 

 them. In order to enable the Committee to carry out this work 

 they begged to be re-appointed. 



Keporton the Conditions under which Liquid Carbonic Acid exists 

 in Rocks and Mimrals, by W. N. Hartley, F.R.S.E.— In a 

 paper read at the Glasgow meeting of the Association, Mr. 

 Hartley described the method of dstermining the exact tempera- 

 ture at which the caibonic acid sometimes found inclosed in 

 minerals becomes gaseous. This temperature is called by Prof. 

 Andrews the critical point, and has been determined by him in 

 the case of pure carbonic acid prepared artificially to be 30" '92 C. 

 Mr. Hartley gives a table showing the critical point of carbonic 

 acid inclosed in various minerals in which certain variations from 

 Dr. Andrews' number are apparent ; these, however, may be 

 accounted for when the critical point is below the normal point 

 by the carbonic acid being mixed with some incondensible gas 

 like nitrogen. 



It seemed desirable to ascertain whether the presence of liquid 

 carbonic acid in rocks was not of frequent occurrence, and 

 whether the immense number of cavities dispersed through 

 various minerals which are usually considered to contain water 

 may not often contain liquid carbonic acid, or whetlier the occur- 

 rence of this body is characteristic of certain formations. A 

 considerable number of minerals was examined, including 

 sapphires, zircons, garnets, topazes, and sections of fluor spar. 

 Incidentally the inquiry led to some very interesting results 

 concerning the motion of the bubbles in fluid cavities when 

 influenced by some source of heat, of which the following is a 

 summary : — ■ 



1. The bubbles in certain fluid cavities approach a source of 

 heat brought near them. 



2. The bubbles in certain cavities [recede from the source of 

 heat. 



3. That 5° C. rise of temperature suffices to cause the apparent 

 attraction. 



4. That a rise of \f C. will in some 'cases cause the apparent 

 repulsion. 



5. That in certain cases a bubble which receded from the 

 source of heat at ordinary temperatures approached it when raised 

 to Co' C. ; the source of heat always being from A" C. to 5° 

 warmer than the specimen. 



6. That this could occur in cavities containing liquid carbonic 

 acii' as well as water, but that it made no diflference whether the 

 carbonic acid was raised above its critical point or not. 



Mr. Hartley ^ has also examined a remarkable vibration of 

 minute bubbles in fluid cavities first noticed by Mr. Sorby. 

 It was found that these bubbles approached a warm body 



