ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 41IJ 



in a diaphragm of vegetable parchment, and then sewn up in a linen 

 cloth. The cell is filled with pure water, and 400 grammes of 

 sulphate of copper placed in the upper part. Thus charged, the 

 battery will act during 24 hours, and these may bo taken either 

 all together or at different times, the battery losing nothing of its 

 charge when it is not employed. When the battery is discharged 

 (which may be known by the liquid becoming colourless) a third of 

 the liquid is removed by an indiarubber tube and replaced by pure 

 water and a new charge of sulphate of copper as before. 



The author then treats of the storage of the electricity, and 

 gives a woodcut of an " acctimulator " made by E. Eegnier on the 

 Plante-Faure system. It consists essentially of two plates of lead, 

 coated with a thick layer of minium, separated, wrapped in flannel, 

 rolled upon themselves, and placed in a glass cylinder, well closed, 

 and containing water acidulated with 10 per cent, of sulphuric 

 acid. On leaving off work in the evening a series of these accumu- 

 lators can be connected with the battery and left until the following 

 evening, and a sufficient amount of electricity will have been stored 

 up for further use. 



The third point dealt with is lamps. The arc light is inadmissible, 

 and only the incandescent lamps can pi'oj)erly be used. Those not in 

 a vacuum are very good for photo-micrography, but are too brilliant 

 for ordinary work. Of incandescent lamps in a vacuum or rarefied 

 medium (Swan, Edison, and Maxim) the author prefers those of Swan, 

 which can bo worked with a force much less than the Maxim lamps. 

 He obtained from Newcastle some special lamps, eminently suitable 

 for microscopical researches, and now employs those exclusively. 

 They are nearly spherical, and are about 3 cm. in diameter, giving a 

 brilliant light with very little expenditure of force. For obtaining 

 a beautiful white light 5-7 Tommasi elements or 3 or 4 accumulators 

 are sufficient. The 4 accumulators will feed the little lamp for more 

 than 12 hours, and a permanent light could therefore be obtained by 

 putting the battery in operation once or twice a week. 



The above details refer, as will be seen, to the Tommasi battery. 

 In the note as to the new battery the author only says " for the little 

 microscope Swan lamps, 5 Eegnier elements and an accumulator 

 must be employed." 



The advantages to be obtained from the emjjloyment of the electric 

 light by the microscopist are of two kinds, which the author classifies 

 under the head of " Illumination of the Microscope " and " Photo- 

 micrography." As to the first, he says that " The incandescent 

 electric light surpasses all other illumination. It has the softness of 

 a good petroleum lamp, and shows delicate details nearly as well as 

 monochromatic light. The delicate striae of Amp}d]jileura and the 

 19th band of Nobert's test are seen with perfect sharimess. Professor 

 Abbe, to whom we communicated the result of our researches, attri- 

 butes it to two causes, 1st, the much greater whiteness of the light ; 

 consequently it contains more blue and violet rays. But, as it has 

 been demonstrated by the measurements made by the I'rofcssor with 

 different monochromatic lights, that the resolving-power of an 



