512 Chronicles of Science. [July, 



The Microscope. 



Dr. Beale lias described to the Boyal Society a new object-glass, 

 with a magnifying power double that of a twenty-fifth. This is a 

 fiftieth, and magnifies nearly three thousand diameters with the low 

 eye-pieces. Messrs. Powell and Lealand, the makers, produced a six- 

 teenth in 1840, and a twenty-sixth in 1860. The fiftieth defines even 

 better than the twenty-fifth, which is now made instead of the twenty- 

 sixth. Plenty of light for illuminating the object to be examined is 

 obtained by the use of a condenser provided with a thin cap, having an 

 opening not more than the thirtieth of an inch in diameter. The pre- 

 paration may be covered with the thinnest glass made by Chance, of 

 Birmingham, or with mica, and there is plenty of room for focussing 

 to the lower surface of thin specimens which can alone be examined 

 by high powers as transparent objects. Particles too transparent to be 

 observed by a twenty-fifth are distinctly demonstrated by the fiftieth ; 

 and Dr. Beale is of opinion that by the aid of those high powers 

 the further careful study of the development and increase of some of 

 the lowest organisms, and the movements which have been seen to occur 

 in connection with certain forms of living matter, as Amoeba, white- 

 blood corpuscles, young epithelial cells, &c, will lead to most valuable 

 results. The finest nerve fibres ramifying in the cornea and in certain 

 forms of connective tissue are also beautifully brought out by this 

 power, and their relation to the delicate processes from the connective 

 tissue corpuscles can be more satisfactorily demonstrated than with 

 the twenty-fifth. The advantage of the fiftieth in such investigations 

 seems mainly due to its remarkable power of penetration. The an- 

 gular aperture of this glass is 150°. Many twelfths have been made 

 with a higher angular aperture, amounting to 180°. 



At the Microscopical Society Mr. Huggins has read a paper " On 

 the Prismatic Examination of Microscopical Objects." The micro- 

 scopists can hope to profit by prismatic analysis only in the case of 

 those substances which modify the light by a special absorption either 

 during transmission or reflexion. But the discoveries of Professor 

 Stokes in connection with the optical character of blood and chloro- 

 phyll, show that even this restricted field of investigation is one of 

 considerable promise. By means of the prismatic microscope, the 

 spectrum of any part of a microscopic object can be examined apart, 

 and also can be compared with the spectra of the adjoining parts of 

 the same object. Thus the spectrum of a single blood disc or of the 

 contents of a single cell can be observed, and changes in living tissues 

 which cause a modification in the spectrum can be watched and inves- 

 tigated. Microscopic physiology may receive some aid from this way 

 of using the prism, since the deepest object-glasses, even the fiftieth, 

 may be employed. The spectra of the light reflected from different 

 parts of the opaque object can be separately examined. The plan con- 

 sists essentially in placing the slit of an ordinary spectrum apparatus 

 in the position usually occupied by the eye-piece of the microscope. 

 Behind the object-glass, at a distance of three or four inches, an ad- 

 justible slit is placed, and the object-glass is focussed upon the object, 



