1881.] 



MICROSCOPICAL JOURNAL. 



11 



extract. It is not very old, but who 

 doubts to-day the possibility of re- 

 solving A. pellucida ? — Ed.] 



Yes, you have under your eyes the 

 despair of microscopic amateurs, the 

 illustrious, Amphipleura pellucida. 

 At first sight, this corpuscle seems 

 quite insignificant, but one should 

 know, that upon these little elongated 

 valves, terminated with double ended 

 extremities, and showing a separating 

 line in the middle, there are horizon- 

 tal striae of an unheard of fineness, 

 to such a degree even that most mi- 

 crographers deny absolutely their ex- 

 istence. And truly, the most powerful 

 apparatus of mine had failed to show 

 them to me, until one fine day I suc- 

 ceeded in obtaining the one-fifth inch 

 objective of the celebrated American 

 constructor Tolles. These lenses have 

 the reputation of being endowed with a 

 force of penetration (resolution ?) and 

 definition unparalleled, so, profiting 

 by the first white clouds which showed 

 themselves on the horizon, I made 

 an essay, and judge of my surprise, 

 when thus, without difficulty, I was 

 able to distinguish perfectly these 

 phenomenal striae whose existence 

 has been so controverted. 



Doctor Hartnack laughed till the 

 hot tears ran down his cheeks, when 

 I told him of this discovery ; he said 

 I was the dupe of my imagination, 

 that I saw with the eye of faith, and 

 that there were no more striae there 

 than upon his hand. 



I renewed the observation under 

 identical conditions and always with 

 the same results. I could no longer 

 doubt. It was a great consolation to 

 me when Dr. Woodward announced, 

 M.M.J., September, 187 1, that he 

 had made the same discovery, and with 

 the same one-fifth inch of Tolles. 



It remains now to be explained 

 how an objective attaining at its 

 maximum an enlargement of 200 

 (300 ?) diameters only, can bring out 

 details of what another, ten to fifteen 

 times more powerful, cannot give the 

 slightest idea. Of all the problems of 



the microscope, this is the most diffi- 

 cult to resolve. Doubt can then no 

 longer be permitted, and Dr. Hart- 

 nack will have his fine laugh and will 

 be forced to yield to the evidence, 

 and make the ai?iende honorable. 



Studies of Atmospheric Dust. 



A long summary of tlie researches 

 of M. Pierre Miquel on the "Or- 

 ganized Dust of the Atmosphere " 

 has been running through several 

 numbers of Brebissonia. The 

 second part begins vv^ith a consider- 

 ation of the " Schizophytes of the 

 Atmosphere," and sincfe many 

 workers with the microscope find 

 great difficulty in distinguishing 

 between Bacteria, Vibriones, Spir- 

 illse, etc., the following free transla- 

 lation from this portion of the paper 

 may be of use to them. 



In his last memoir on the Schizo- 

 phytes, M. Cohn has given a botan- 

 ical classification of bacteria and 

 vibriones. The classification pub- 

 lished by this German savant in- 

 cludes no less than fifty species and 

 several hundred varieties. The at- 

 mosphere, which may on certain 

 occasions, become the vehicle of 

 all these organisms is, however, far 

 from presenting to analysis the great 

 number of various forms which 

 multiply in exposed infusions. 

 There are spores of bacteria and 

 also of moulds; certain of them 

 are constantly presented to the eyes 

 of the observer. The liquids which 

 are sown with dust from several 

 litres of air rarely become peopled 

 with organisms of greatly varied 

 forms ; almost always one finds Mi- 

 crococcus and Bacillus^ which seem 

 to have a mission to mask the mi- 

 crobes which one desires to discover 

 among the particles of dust carried 

 by the wind. To enter upon the 

 study of the bacteria of the atmos- 

 phere, therefore, it is not necessary 



