SCIENCE. 



541 



Fig. 6. — Mounting of the Edison machine. 



the lights with alternate currents produce a peculiar hum- 

 ming owing to the nature of the currents which traverse 

 them ; this humming is often sufficient to forbid their use 

 in places where it is necessary to have comparative silence. 



The ensemble of a system of lighting by dynamo-elec- 

 tric machines, with alternative currents always includes 

 two distinct machines : a machine with continuous cur- 

 rents or generator ; and a machine with alternate currents, 

 or distributor. J his distributor consists of a variable 

 number of circuits. Figure 8, simplified to show the 



Fig. — Mounting of a machine with alternate currents for candles. 



principle, represents the mounting of a Gramme machine 

 with alternative currents, supplying twenty Jablochkoff 

 candles, arranged on four circuits of five candles each. 

 The movable inductor bears eight poles, the successive 

 ones with contrary names, in place of four. The gen- 

 erator can be of any system, whatever ; it is only neces- 

 sary to have a continuous current. 



The power is regulated by the reciprocal velocities of 

 the generator and the distributor. Sometimes the two 

 machines mounted on the same axis turn with the same 

 velocity, forming in reality but one. These machines are 

 self-generators. In this case, we can no longer regulate 

 the generator by its velocity, since this velocity is con- 

 jointly acting with the distributor ; the regulating is then 

 effected by the resistances introduced in the generating 

 circuit. We have supposed the inducted bobbins fixed. 

 and the inductors movable. It is the case with the 

 Lontin, Gramme, and Lambotte-Lachaussee machines. 

 At other times, as in the Wilde and Siemens machines 

 with alternate currents, the inducted bobbin is movable 

 and the inductors fixed, but nothing is changed for this in 

 the general principle. We see from these several examples 

 that the art of the engineer allied with the science of the 

 experimentalist, offers some resources to convert me- 

 chanical energy into electric energy and then to distribute 

 it to the lights which utilize it. 



MICROSCOPISTS. 

 The first meeting of the State Microscopical Society of 

 Illinois, for the present season was held at the rooms of 

 the Society, in the Academy of Sciences, Friday evening 

 October 14, the President, Dr. Lester Curtis in the 

 chair. 



After the transaction of routine business, Mr. Stuart 

 described the microscopical structure of some vegetable 

 drugs. The subject is not suitable for abstraction, and 

 requires illustrations to be usetul. 



His paper was followed by one by Dr. Curtis, describ- 

 ing a new stand made for him by Bulloch. This stand 

 presented some novel features, among the most striking 

 was a mechanical stage of extreme thinness, admitting 

 light at an angle of 160 . The movements were effected 

 by a double pinion above the stage, an arrangement pro- 

 nounced by those familiar with the operation of the con- 

 trivance, as exceedingly useful and convenient. 



The stand excited considerable interest, as did also a 

 right angled camera lucida of German manufacture 

 which was adapted to it, the superiority of which over 

 the ordinary form was so marked as to be unmistakable 

 on trying it, even under the disadvantages of a crowded 

 room and constant jar. After a discussion of the papers, 

 the meeting adjourned. E. B. Stuart. 



Secretary pro tern. 



PERMANGANATE OF POTASH USED AS AN 

 ANTIDOTE TO THE POISON OF SERPENTS. 



Very interesting experiments have been made in Bra- 

 zil, by M. de Lacerda, which have established the fact 

 that permanganate of potash is one of the most energetic 

 antidotes to the venom of snakes. M. de Lacerda has 

 addressed a memorial of his important works to the 

 Academy of Sciences (meeting of the 12th of Septem- 

 ber, 1881). 



The result of these researches is really astonishing ; thus 

 in a series of experiments, frequently renewed, ot inject- 

 ing the active venom of boshrops, diluted with distilled 

 water, in the cellular tissues, or the veins of dogs, M. de 

 Lacerda found that the permanganate of potash was able 

 to stop completely the manifestation of local injuries 

 from the venom. Yet the same poison, which had served 

 for these experiments, being injected without antidote 

 into other dogs, always produced great local tumefac- 

 tions, with loss of substance and destruction of tissue. 



These very remarkable results have been stated on va- 

 rious occasions, not only by the Emperor of Brazil, who 

 assisted at these experiments, but also by physicians, 

 professors of faculties, and members of the diplomatic 

 corps. 



Means of Detecting the Sophistications of Olive 

 Oil with other Oils. — The oils employed at Marseille for 

 the adulteration of olive oil are the oils of colza, sesame, 

 cotton, and earth-nuts, Colza oil is detected by means of 

 the sulphurwhich it contains; 10 grms. of the sample are 

 saponified in a glass capsule with an alcoholic solution of 

 caustic alkali free from sulphides. The mixture is stirred 

 with a silver spoon, and if this is blackened, colza, or at 

 least some cruciferous, oil is present. For the detection of 

 the oil of sesame a little sugar is added to hydrochloric 

 acid at 30° (Baume?) which is then mixed with an equal 

 bulk of the oil in question. The mixture is well shaken 

 up, and the least traces of oil of sesame are indicated by 

 a red coloration. For the detection ot cotton-seed oil there 

 is added to the sample an equal volume of nitric acid at 40 . 

 On stirring the mixture takes a coffee color. The detection 

 of oil of earth-nuts is less simple. The sample is saponi- 

 fied with an alcoholic solution of potash, the soap separated 

 as completely as possible, heated to expel the alcohol, and 

 treated with enough hydrochloric acid to neutralize the 

 alkali. The supernatant fatty acid — arachidic acid — is col- 

 lected and dissolved in boiling alcohol, from which it sepa- 

 rates in a characteristic white nacreous form. 



