1883.] 



MICROSCOPICAL JOURNAL. 



119 



— A receipt for dammar varnish is given 

 in Science Gossip as yielding a solution 

 that will remain perfectly limpid. Add 

 8 fl. drachms of pure benzole to 4 drachms 

 of crushed Indian dammar, and allow sol- 

 ution to take place without applying heat. 

 Decant the clear fluid from the insoluble 

 residue, and add to it 80 minims (i^ 

 drachms) of spirits of turpentine. The 

 purpose of the turpentine is to make the 

 varnish tough. * The addition of mastic is 

 of no value. 



— Dr. Van Ermengem has obtained a 

 preparation of }s.OQ\\?,Bacillus tuberculosis 

 by tiltering the air expired by a consump- 

 tive patient through gun cotton. By 

 dissolving the latter in ether the bacillus 

 was obtained, and stained by a proper 

 method for demonstration. 



— It has long been an opinion among 

 microscopists that the best and strongest 

 light for the illumination of microscopic 

 objects is obtained by substituting a 

 prism for the ordinary mirror. The ad- 

 vantages offered by the prism are more 

 theoretical than practical, while the quan- 

 tity of hght reflected by a silvered mirror 

 is far greater than can be obtained from 

 a prism of equal size. The only advantage 

 of the prism is the reflection from the 

 single plain surface, while the mirror gives 

 a reflection from both the outer and inner 

 surfaces of the glass. But practically 

 this is of absolutely no consequence. A 

 well-silvered mirror reflects 95% of the 

 light incident upon it. We will soon 

 give a process for silvering glass which 

 yields perfect results, and is readily 

 applied by any person. 



— Mr. E. C. Hansen has been studying 

 the distribution of germs in the atmos- 

 phere, with reference to their influence 

 upon fermentation in the manufacture 

 of beer. He finds that the organisms 

 in the air occur in swarms or clouds, 

 with the intervening air quite free from 

 spores. About the time of ripening 

 of fruits the germs are most abun- 

 dant. Under cherry trees, when the 

 fruit was ripening, the yeast-fungus was 

 found abundant in the air, while under 

 grape vines, at the same time ( the grapes 

 not being ripe), the spores were not 

 formed. In good fruit years the air is 

 most full of germs. The air in one malt 

 house was found to be more free from 

 sporules than the air outside — probably 

 owing to the fact that the air was cooled 

 and washed with a shower-bath of salt. 



In other malt-houses the mould-fungi 

 were very abundant in the air. These 

 fungi exert a great influence upon the 

 result of fermentation. 



— Dr. A. RoUet has devised what 

 seems to be a valuable instrument for 

 spectroscopic research. It is to be used 

 for examining objects in monochromatic 

 light, and for the study of their properties 

 of double refraction. It consists of a 

 combination of a polarizer and a spectro- 

 scope beneath the prism and an analyzing 

 prism above the ocular. 



— Prof. Abbe's new camera lucida is 

 essentially the same as the new form 

 lately devised by Mr. Grunow ; but in 

 Prof. Abbe's form the image of the pen- 

 cil and paper is reflected to the prism 

 over the eye-piece from a mirror sup- 

 ported by an arm which extends some 

 distance from the ocular, so as to clear 

 the base of the microscope. 



— Mr. Aug. Gruber has described a 

 new form of amoeba — Aviccba obtecta — 

 which, not having any true shell, never- 

 theless forms a hemispherical case in 

 which it lives, and extends its pseudopo- 

 dia in all directions. We presume it 

 should properly be classed among the 

 forms with a shell, but the author has 

 placed it in the germs Aniceba. 



— We have already referred to a new 

 form of fine-adjustment recently per- 

 fected by Mr. Wenham and introduced by 

 Messrs. Ross & Co. Mr. Swift has also 

 introduced a very simple and effective 

 fine-adjustment, on a different principle, 

 which we believe is totally new. The 

 adjustment-screw is on the left of the 

 limb, moving horizontally and working a 

 long vertical lever having a short arm at 

 right angles at the top, which imparts a 

 vertical movement to a rod attached to 

 the nose-piece carrying the objective — 

 not moving the main tube at all. It 

 works admirably, and is a very cheap 

 contrivance. 



CORRESPONDENCE. 



Fission of Hydra. — In the April 

 number of the American Monthly Micro- 

 scopical Journal ( vol. iv. p. 64.), Mr. T. 

 B. Jennings notices a case of reproduc- 

 tion by fission in Hydra. Such cases 

 are very rare but they have been noticed 

 by Trembley, Rosel and Marsh all, the 

 latter having seen three cases of this 

 process. J. S. Kingslev. 



