370 



NATURE 



\_August 30, 1877 



after a period of two months ; and for pocket-chrono- 

 meters, r57 sec. after a trial of six weeks ; and the 

 average differences between the maximum and minimum 

 rates proved to be, for box-chronometers, 3'23 sec, after 

 a two months' trial ; and for pocket-chronometers, 6'2 2 sec. 

 and 575 afcer six weeks and one month's trials. These 

 figures show certainly that there is enough to do yet in 

 raising the industry to the high degree of perfection which 

 is desirable, but the steady progress during the last ten 

 years is remarkably seen in a table showing the increase 

 of precision of the Swiss chronometers in every direction. 

 Thus the average diurnal variation, which was as high as 

 1-27 sec. at the competition of i8(j4, regularly decreases 

 to o'46 in 1S75 ; the average variations of rate produced 

 by changes of position, being 82 1 sec. ten years ago, is 

 now but I 97 ; and the defective compensation for tem- 

 perature rapidly decreases from o'48 sec. for each degree 

 to 01 6, and now it is but o'i3. Besides, the report states, 

 some of the best chronometers reach as high a degree of 

 perfection as to make them comparable with astronomical 

 clocks. Thus the box-chronometer which received the 

 first prize is a true phenomenon of its kind. Its mean 

 diurnal variation is as low as ooS sec, i.e., that of good 

 astronomical clocks ; its mean weekly rate chang;ed after 

 a two months' trial only by 0-57 sec. ; the difference 

 between the maximum and minimum rates is but o 94 sec, 

 and the imperfect compensation for temperature is 

 004 sec. for each degree ; finally, its characteristic 

 number, calculated by the Greenwich method, reaches 

 but 8'90 sec. The two best pocket-chronometers realise 

 perhaps a yet greater success, their average diurnal 

 variations being respectively but o'i3 and o'i7 sec. 



THE BRITISH ASSOCIATION 



THE two soirees that were held in the Guildhall, the 

 first on the evening of Thursday, the i6th instant, 

 and the second on Tuesday, the 21st, were very fully 

 attended. 



At the second conversazione several objects of scientific 

 interest were exhibited. At the centre table Prof. Herbert 

 McLeod showed his beautiful cycloscope, an instrument 

 which formed the subject of a paper read by Prof. McLeod 

 before Section G on Wednesday week. Mr. Silvanus P. 

 Thompson, of University College, Bristol, showed his 

 apparatus for exhibiting certain optical illusions, upon 

 which a paper was read by him in Section A. Prof. 

 Osborne Reynolds showed the apparatus by which his 

 paper upon the rate of progression of groups of waves 

 was illustrated ; and Mr. J. VV. Swan exhibited a modifi- 

 cation of the Sprengel pump. 



In the picture gallery Dr. Graham Bell had his articu- 

 lating telephones at work. 



There was great competition for the tickets for the 

 excursions for both Saturday and Thursday. The excur- 

 sion to Lee Moor under the guidance of Mr. Spence 

 Bate, F.R.S., was originally limited to 100, but there were 

 more than 300 applications for tickets, and extra 

 waggonettes had to be put on. The party, after having 

 visited the China Clay Works of I\Iessrs. Martin, the 

 largest establishment of its kind in the world, divided 

 into three parties : the first walked across the Moor to 

 Sheepston, to examine some prehistoric remains recently 

 discovered by Mr. Spence Bate. Another party under 

 the charge of Mr. Martin took a walk to Shell top and 

 Pen Beacon, from which fine views may be had ; and a 

 third detachment remained in the grounds of Mr. Martin, 

 which are unique in their way, from the intricacy of their 

 laying out. 



The popular excursion of the day was, however, that 

 up the Hamoazeand Tamar, to H.M.S. Caiiibrid'j^c, under 

 Great Albert Bridge at Saltash, into the Sound, and 

 visiting the Breakwater and Eddystone Lighthouse. 



The Admiral of the Port placed three (iovernment 

 steamers at the disposal of the Association, and there was 

 tremendous crowding to get on to the boats. Upon 

 reaching H.M.'s gunnery ship Cambridge, the gunnery 

 and torpedo practice began, and some splendid feats of 

 firing at long ranges were exhibited. 



On the same day there was a dredging excursion under 

 the superintendence of I\Ir. Gwyn Jeffreys and Mr. 

 Hearder. 



While these excursions were going on a select party 

 was, at the invitation of the Mayor and Corporation of 

 Exeter, visiling that ancient city. At the luncheon, the 

 toast of " The liritish Association," was proposed by Sir 

 Stafford Northcote, Chancellor of the Exchequer, and 

 responded to by Mr. Spottiswoode, F.R.S., the Presi- 

 dent-elect. 



The excursions on Thursday last were first to Liskeard, 

 the Cheesewring, and the Caradons, at the invitation of 

 the Mayor of Liskeard. The second excursion was 

 by way of the Tamar to Morwellham to the celebrated 

 Devon Consols Copper Mines, taking on its way the 

 fine old medieval mansion of Cotehele, which was 

 thrown open to the members by the Earl of Mount 

 Edgcumbe, to whom it belongs. The last of Thursday's 

 excursions was to Totnes, Torquay, and Brixham, 

 and like the Exeter excursion, was only by special 

 invitation. It was divided into four sub-excursions 

 («), Archaeological, visiting Totnes and Berry Pomeroy 

 Castles ; iji), Mechanical, visiting the Experimental 

 Works of Mr. Froude, F.R.S. ; and (c and d), Anti- 

 quarian and Geological, the first to Kent's Cavern, under 

 the guidance of Mr. Vivian, and the second to Brixham, 

 with Mr. Pengelly, F.R.S. 



The Plymouth meeting of the British Association for 

 1877 has b;en decidedly a quiet one ; its attendance as a 

 whole has been below the average, and its funds are pro- 

 portionately low ; but it has done good work, and it has 

 been marked by several papers of great scientific interest. 

 The discovery by Prof. J. C. Adams of the original papers 

 of Newton respecting the rotation of the apse of the 

 moon, the exhibition of the articulating telephone of 

 Dr. Graham Bell and the very valuable suggestions con- 

 tained in the address of Prof. Carey Foster, must all help 

 to mark the Plymouth meeting in the annals of the 

 Association as a valuable one, notwithstanding its failure 

 in points of attendance and pecuniary position. 



The following are some of the figures connected with 

 the recent m-eeting : — 



Number of tickets issued to Old Life Members ... 161 



New ,, ,, 19 



,, ,, ,, Old Annual Subiciibers 238 



,, ,, ,> New ,, ,, ... 58 



,, ,, ,, Associates 447 



,, ,, ,, Ladies 2S3 



There were also present, of Foreign Members 11 



Making a total of 1,217 



The total receipts from the sale of tickets amounted to 

 1,267/. 



REPORTS. 



Prof. O. Reynolds presented the Rj/'ivl of tlu- CoinmUtec ap- 

 foiitled to consider what Effect Kevening tin Screw had on the 

 Steering of a Steamer under Full Way. — Since the last meeting 

 of the Association the Committee had carried out further experi- 

 ments, and the results now obtained show that the larger the 

 ship the more important the effect of reversing the screw became. 

 In answer to the request of the Committee, the Admiralty had 

 made a trial with H.M.S. SfieeJy, but the conditions under 

 which it was conducted precluded tlie possibility of more light 

 being thrown on thesubject. The greatest speed was five knots, 

 and the effect of the rudder witli the screw reversed w.as so small 

 that the vessel in most instances turned her forward end into the 

 wind. Tlie Admiralty had been urged to have experiments made 

 with larger and more powerful ships, but as yet had not assented 



