1880.] 



MICKOSCOPICAL JOUEKAL. 



239 



seen in any other glass, and especially in 

 any other 4-10. I can commend this 4-10 

 to any one who, like myself, is too poor to 

 go up higher, and with a 2-inch of 12°, a 

 2^ of 27°, and this 4-10 of 110°, I am 

 equipped for a large scope of work. I do 

 not believe that one can do every thing 

 with a 4-10, but it seems to me that until 

 one can afford to go up to a ^ of 1.40 

 like the one I used the other night, he can 

 feel very rich with these. 



S. A. Webb. 



To THE Editor : — In determining the 

 value of the spaces of an eye-piece mi- 

 crometer by seeing how many of its spaces 

 are covered by one space on the stage- 

 micrometer, I find that I get the same re- 

 sult by using the " A " eye-piece that I do 

 by using the " B " eye-piece. 



The eye-piece micrometer used was one 

 of Zentmayer's disks, and the stand one 

 of his " Histological " stands. 



If you will publish an explanation in 

 your next magazine, you will much oblige 

 several of your subscribers. 



K. 



[Doubtless many others have observed 

 the fact mentioned by our correspondent. 

 The explanation is that the relation be- 

 tween the field-lenses of the two oculars 

 is such that the rays from the objective 

 are bent out of their original course to 

 just such a degree that the eye-lenses 

 magnify the image of the stage microme- 

 ter in about the same pro-portion as they 

 do the spaces of the eye-piece microme- 

 ter. By consulting the table on page 207 

 it will be seen that the relations between 

 the field and eye-lenses are not the same 

 in all instruments, and therefore the ob- 

 servation of our correspondent would not 

 always be true. — Ed.] 



NOTES. 



— The interesting discovery of haemo- 

 globin in the aquiferous system of an 

 Echinoderm — Ophiactis virens — has 

 been announced by M. Foettinger. The 

 coloring matter was distinguished by the 

 spectroscope as oxyhasmoglobin ; it oc- 

 curs in nucleated cells, and also in others 

 not nucleated. 



— Considerable attention has lately 

 been given to the influence of light upon 

 the movement of plants. E. Stahl has 

 observed that sometimes the chlorophyll 

 grains move within the cells, while at 



other times the entire cells place them- 

 selves in certain positions as regards its 

 direction. Swarm-spores usually turn their 

 anterior end toward weak light, but re- 

 verse this direction when the illumina- 

 tion is stronger. When a filament of 

 Vaucherza is illuminated with light of 

 a certain intensity, it grows at a right 

 angle to the direction of the rays, but if 

 the light becomes less strong, the plant 

 grows directly toward it. 



— In the course of some investigations 

 on the pathology of anthrax. Prof. W. S. 

 Greenfield was led to observe that the 

 Bacillus ant/iracz's lost its power of com- 

 municating the disease by inoculation, 

 after cultivation through successive gen- 

 erations in a nutrient fluid (aqueous hu- 

 mour). The disease was never produced 

 by any generation after the twelfth. The 

 morphological characters of the organ- 

 ism remained unaltered. 



—Messrs. George P. Rowell & Co. 

 have favored us with a copy of the 

 American Nawspaper Directory for 

 1880. It is a large, elegantly bound volume 

 of over one thousand pages, and contains 

 much concise information for advertisers 

 and pubHshers. The publishers give 

 some interesting figures in regard to the 

 magnitude of the work of collecting the 

 information about newspapers. This is 

 the twelfth annual issue, of which over 

 ten thousand copies have been printed, at 

 a cost of over $12,000, indicating that the 

 advertising business of that firm must be 

 very great. 



— We have received some very inter- 

 esting and rare slides from Mr. John 

 King, of Cincinnati, who has given spe- 

 cial attention to the preparation of crystals 

 of the alkaloid Hydrastia for use with the 

 polariscope. Hydrastia may be dissolved 

 in alcohol and the solution evaporated on 

 the slide, but the best way to obtain beau- 

 tiful crystals for the polariscope is to fuse 

 a portion on the slide, and place the cover 

 over it before it cools. Although it is said 

 to be somewhat difficult to prepare good 

 slides of this material, it is certainly ca- 

 pable of yielding very brilliant effects, as 

 Mr. King's slides conclusively prove. 



— Professor Chester has sent us a slide 

 of gold-crystals, mounted according to the 

 method which he describes in this num- 

 ber. The slide presents a very pleasing 

 appearance, and leaves nothing to be de- 

 sired in this respect. The crystals of gold 

 prepared by Prof. Chester are very beau- 

 tiful, under the microscope, especially 



