i8S2.] Microscopy. 691 



describes the modes of occurn 



Diamonds occur in gravel, in 



compact quartzite conglomerate, and in their original matrix in 



veins traversing the hydromica schist and itacolumite formation. 



The diamond-bearing veins are decomposed hydromica schists 



underlying the itacolumite. By making use of the polarizing 



microscope of Bertrand, Descloiseaux has been able to determine 

 the crystallographic and optical characters of nadorite, and has 



shown that the crystals are twins. Rocksalt of a bright 



green color has been found in the Douglashall shafts. It con- 

 tained 59 per cent, of potassium chloride with enclosed crystals 

 of potassio-ferrous chloride (2KCI, FeCL, 2 FLO), for which 



Ochsenius has proposed the name " douglasitey A specimen 



of chalcedony recently brought by Mr. P. Rathbone, from Monte 



Video, contains an ounce of liquid, with a large bubble. 



An apple green, clayey substance occurs in crevices in the 

 weathered granite of Upper Austria, which becomes brittle upon 

 exposure to the air, and falls to pieces in water. It is essentially 

 a hydrous silicate of alumina, and appears to be similar to the 



variety of fuller's earth, known as razumoffskin. O. Leudecke 



has studied the fireblende (pyrostilpnite), of Andreasberg, and 

 finds its composition identical with that of pyrargyrite. As the 

 former is monoclinic, and the latter rhombohedral, Ag :1 SbS 3 is 

 proved to be dimorphous. 



MICROSCOPY. 1 



The August Meetings. — The Elmira meeting of the American 

 Society of Microscopists, August 15-18, and the Montreal meeting 

 of the A. A. A. S., August 23-30. will both be occasions of un- 

 usual interest, and all persons interested should attend one or 

 both if possible. At Montreal the new section of histology and 

 microscopy will meet for the first time, as a full section and with 

 the same standing as the oldest and most important sections of 

 the association. 



Eye Protectors.— Nearly every one who has used the monoc- 

 ular microscope to any extent has experienced a peculiar fatigue, 

 due to the unequal use of the two eyes, which is felt most in the 

 unused eye, and which is about equally troublesome whether 

 that eye be kept open and confused by a useless vision, or closed 

 and irritated by the sudden and frequent changes from use to dis- 

 use and by the unnatural muscular efforts required to accomplish 

 this. In most cases, as is well known, if this process be con- 

 tinued long enough, the disused eye becomes comparatively 

 worthless, and the person works almost exclusively with one eye, 

 whether with the microscope or without it. A similar effect has 

 been noticed in the habitual use of the telescope and other optical 

 instruments.. Persons are often obliged, after some years, to 

 Practice using the left eye chiefly, for the sake of restoring as far 



1 This department is edited by Dr. R. H. Ward, Troy, X. Y. 



