208 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



A SIMPLE METHOD OF ILLUMINATING OPAQUE 



Objects under High Powers. — In the " Journal of 

 the Royal Microscopical Society," for June, Mr. James 

 Smith describes an easy method of illuminating 

 opaque objects under the higher powers of the micro- 

 scope. The microscope is placed in position for 

 observation with the light in front (or at the side, as 

 may be most convenient), about three inches off the 

 flame, which should be somewhat lower than the | 

 stage, and turned edgewise to the microscope. The : 

 bull's-eye condenser is then placed between the stage 

 and the lamp, with the plane side uppermost, the 

 convex surface being a little higher than the stage. 

 The light strikes the plane surface of the condenser, ' 

 and is again reflected at a very oblique angle upon 

 the object on the stage, a sharp and brilliant wedge 

 of light being cast upon the slide. The position of 

 the lamp and condenser requires some careful adjust- 

 ment to produce the best effect, when it will be 

 found to answer all practical purposes for ordinary 

 use. There is, however, a slight haziness (such at 

 least is my experience) caused by the cover-glass. 

 Probably the effect would be better on uncovered 

 objects. The method, however, is so simple and 

 inexpensive that it is well worth being noticed. I 

 have seen pollen-grains and butterflies' scales viewed 

 as opaque objects under a 1th and ~th as I have never 

 been able to see them with any other method of 

 illumination. — R, IT. Nisbett Browne. 



The Fresh-water Rhizopods of North 

 America. — Thanks to the kindness of the United 

 States Government, we have received a copy of this 

 elaborate and beautiful work, by Dr. Leidy. It is 

 one of the series of volumes published by the U.S. 

 Geological Survey. The book opens with a short 

 introduction, in which Dr. Leidy states (in order to 

 give confidence to students) that expensive instru- 

 ments are not required for such investigations as 

 those herein described^; on the contrary, the instrument 

 he has in use is called the " Economic Microscope " 

 (sold by Mr. Beck), and has J-inch and i-inch 

 objectives. The introduction is followed by some 

 general remarks on the Rhizopods, including 

 comments on their classification ; where they may be 

 found ; their collection and examination ; and a short 

 review of the Orders into which they are divided. 

 Dr. Leidy then proceeds to the systematic description 

 of the various genera, &c, and appended to this is a 

 list of the Fresh-water Rhizopods, indicating the 

 many forms which occur together in certain localities. 

 A catalogue is also given of the chief works 

 and communications relating to the Fresh-water 

 Rhizopods, with lists of the forms described, and a 

 partial and probable reference of these to corre- 

 sponding forms described in the body of the present 



work. The whole is followed by a series of forty- 

 eight brilliantly executed plates, lithographed from 

 the author's sketches ; the greater portion are coloured, 

 and all are drawn to scale. Perhaps it will not detract 

 from the interest of the work if we mention the fact 

 that these elaborate researches, extending over a 

 period of many years, have brought no pecuniary 

 recompense to their able conductor. 



The Birmingham Microscopists and Natu- 

 ralists' Union. — This society has been formed to 

 supply a want which has been felt amongst many 

 students of microscopy and natural history, who 

 are desirous of securing the benefits of mutual help 

 and co-operation at the minimum cost ; and to place 

 the society within the reach of all, the subscription 

 has been fixed at $s. per annum. The officers of the 

 new society wish it to be understood that it is not 

 formed in any spirit of antagonism or rivalry to the 

 older and more advanced ^society, the Birmingham 

 Natural History and Microscopical Society ; but 

 it is intended to help more elementary students who 

 are not members of the older society. The president 

 is Mr. J. W. Oliver. 



San Monica Earth. — At a recent meeting of 

 the San Francisco Microscopical Society, the Presi- 

 dent announced, to the great satisfaction of the 

 members of the society, that more of the celebrated 

 " Santa Monica earth," or some similar to it, had 

 been discovered. The deposit is about seventy miles 

 from the spot where the original piece was first dis- 

 covered by Mr. T. P. Woodward two years ago. 

 Professor H . L. Smith, of Geneva, N. Y., reports in 

 regard to this deposit, that he has tried the "new 

 find," and finds it so rich and so nearly like the 

 " Santa Monica," that he desires a quantity, so as to 

 be able to supply the demand. Mr. Norris and ex- 

 President Hyde have also made a careful examination 

 of the material, and the former presented a mounted 

 slide which showed forms of great beauty and fully as 

 rich as the original of two years ago. Scientists all 

 over the world, it is to be hoped, can now be supplied 

 with this very interesting material, for which they 

 have been so anxious. 



Yellow Fever and the Microscope. — Dr. 

 Sternburg, who has been devoting his attention for 

 some time to the natural history of the Yellow Fever, 

 at New Orleans, has announced that " there is no 

 gross and conspicuous germ or organism, either in 

 the blood of yellow fever patients, or in the air of 

 infected localities, which by its peculiar appearance 

 or abundant presence might arrest the attention of 

 a microscopist, and cause suspicion that it is the 

 veritable germ of yellow fever. " This statement is of 

 importance in view of the announcement lately made 

 by Klebs and Tomason that they had discovered what 

 they believed to be the germ of malarial fever in the 

 neighbourhood of Rome. 



