^82 



NATURE 



{April 2\, 1 88 1 



motive force of 30 or even 40 volts between the carbons 

 in the electric arc, but that the actual resistance of the 

 arc is small. 



4. The electro-dynamometer method, the best method 

 fitted for ready measurement, in which the current in one 

 coil is attracted by the same current flowing in another 

 coil, and the attraction is balanced by a spring as in 

 Siemens' s electro-dynamometer, or by weights as in 

 Trowbridge's electro-dynamometer. A beautifully-made 

 instrument by Elliott and Co. was e.xhibited, in which the 

 coils are thick copper bands, fixed coils being placed on 

 each side like the coils of a tangent galvanometer, 

 the suspended coil being placed between them in place 

 of the magnet of the galvanometer. This instrument is 

 especially useful for the measurement of very large 

 currents in absolute measure. 



The remainder of the second lecture was devoted to 

 the consideration of the efficiency of batteries or of mag- 

 neto-electric machines when employed as motors to do 

 work by means of electricity, and it was shown that the 

 greatest amount of effective work is produced when one- 

 half the energy of the battery or current-generating 

 machine is converted into useful work in the electric 

 circuit. Numerous experiments were made with Clarke's 

 and other magneto-electric machines to show that by the 

 same machine work may be produced by sending a bat- 

 tery current through it, causing motion of the armature 

 carrying the current in accordance with Ampere's laws, or 

 a current of electricity may be generated by turning the 

 armature, i.e. by doing work upon the machine, so that 

 a magneto-machine is a reversible engine. A small mag- 

 neto-machine with a Siemens armature was made to work 

 a pump, or when turned by hand produced a current of 

 electricity. Also a battery current in a Gramme ring in 

 front of the poles of a Jamin magnet caused rotation of 

 the ring and turned the heavy driving-wheel of the 

 machine, and on removing the battery and turning the 

 driving-wheel by hand, a cuirent of electricity was pro- 

 duced which caused a piece of platinum wire to glow. 

 Also a Tisley's hand dynamo-machine was emplo)ed 

 either to heat a long piece of platinum wire or to drive 

 another magneto-ekctric machine, so producing a second- 

 ary current capable of heating a coiisiderable length of 

 platinum wire. 



[To be continued.) 



THE FRENCH ASSOCIATION FOR THE 

 ADVANCEMENT OF SCIENCE AT ALGIERS 



Algiers, April 14 

 nPHE number of members enrolled for the present 

 -*■ Congress is much larger than might have been 

 expected when we consider the length of the journey. 

 To a Parisian member this is such as would be ex- 

 perienced by a Londoner if our British Association 

 met in Gibraltar. Yet more than 1500 names are on the 

 list. Few of these are familiar to us. There appear to 

 be an unusual number of doctors and professors of 

 anatomy and physiology, and of civil engineers. We fear 

 we must also confess that a great many people possessing 

 little or no interest m science, who will not be present at 

 a single sectional meeting, have joined the Association 

 for the sake of seeing Algiers. The general character of 

 the meeting appears to be that of a great excursion. 

 There are only five days partially devoted to work ; while 

 the banquets, balls, letes, courses, and " fantasias " are 

 rapidly multiplying. 



On arriving in Paris we were told that the steamer 

 which was to have conveyed us to Algiers had been re- 

 quisitioned by the Government for the transport of troops 

 to Tunis ; but the Company determined at last to take 

 both soldiers and savants, and the result was of course 

 an overcrowded boat and excessive discomfort. With 

 accommodation for fifty first-class passengers no less than 



one hundred and twenty-nine were crowded into the 

 vessel, and had the voyage been anything but of the 

 smoothest, it would have been most wretched. As it was 

 it was bad enough ; the food was insufficient in quantity 

 and detestable in quality, and passengers were glad to 

 find six feet of floor to sleep upon. In Algiers itself the 

 hotels are quite full, and the salons will be used as 

 dormitories. 



The Congress will be opened to-day by the inaugural 

 address of M. Chauveau, which is to be given in the 

 theatre at three o'clock, after which the members will 

 remain and resolve themselves into a general com- 

 mittee to discuss the creation of a sixteenth section relat- 

 ing to pedagogy ; afterwards the secretaries of sections 

 will meet to arrange their proceedings, and at 9 p.m. the 

 members will be received by the Municipality at the Hotel 

 de Ville. The general programme for the rest of the 

 week is as follows : — 



Friday, April 15. — Sectional meetings in the forenoon; 

 general meeting at 2 p.m. ; conference at half-past 8. 



Saturday. — Sectional meetings in the morning; visit 

 to the Algerian Exhibition in the afternoon ; Arab fete, 

 and a soiree given by the Municipality. 

 Sunday. — '' Courses et fantasia." 



Alonday. — Sectional meetings in the morning ; a pro- 

 cession through the town in the afternoon, and an Arab 

 fete in the evening. 



Tuesday. — Sectional meetings ; general concluding 

 meeting ; in the evening a ball given by the Governor. 



On IVednesday the excursions commence ; they are 

 1 oth general and sectional, and the longest lasts for a 

 fortnight. 



A complete list of the papers to be read has not yet 

 appeared, but in the list already published we do not note 

 anything of special interest. 



English science is represented by Dr. G. H. Gladstone 

 and Mr. Siemens, who will both read papers. 



The Association has presented to each member a work 

 in two volumes entitled "Notices scientifiques, histor- 

 iques, et economiques sur I'Alger et Alg^rie." 



April 15 

 The theatre was well filled yesterday afternoon to hear 

 the address of the president, M. Chauveau, who is Pro- 

 fessor of Physiology in the Lyons Veterinary College. 

 His discourse was of a far too technical character to be 

 of interest to the majority of his audience, and dealt 

 principally with the germ theory and Pasteur's theory of 

 fermentation. It was read throughout without the least 

 attempt at oratory, and it contained various political 

 allusions which were much applauded. In the evening 

 the members were entertained by the Municipality, and 

 the town was illuminated. The real work of the Asso- 

 ciation commenced this morning, when the sections met 

 at hours varying from eight to ten o'clock. We fear that 

 the number of papers is small, and that the Association 

 does not represent French science at all completely. In 

 the Physical Section, for example, the names of only two 

 authors of papers appear to-day — MM. Brillouin and 

 Crova. At 9 a.m., when the section was announced to 

 meet, no one was present. Shortly afier«ards the secre- 

 tary arrived, but an hour later the section had not met. 

 The average number of the audience at the sections 

 which had already met did not at this time exceed ten. 



Among the more interesting papers announced for to- 

 day are the following : — M. Marcheray, on Telephonic 

 Communication in large towns ; M. "Tacchini, on the 

 Observatories of Etna and of Chimona ; M. Thoulet, on 

 the Employment of the Microscope in Chemical and 

 Physical Researches connected with Mineralogy; M. 

 Prungrueber, on 300 Anthropological Observations on the 

 Kabyles of the Djurdjura Mountains. 



The Medical and Agronomical Sections have plenty ol 

 communications. The new section of Pedagogy has 

 been established under the honorary presidency of M. 



