224 



THE AMERICAN MONTHLY 



[December, 



quite lost, only a faint tinge of red 

 remaining. The diameter of these 

 cells ranges from 10.8//. to 30;/. 



A specimen was received in Janu- 

 ary of this year from Poverty Gulch, 

 Colorado, sent by Mr. Alexander 

 McDougall. It is numbered in the 

 museum register 74,537. 



From the letter which accompanied 

 this specimen I quote as follows : — 



' Sediment of a small quantity of 

 snow gathered in Poverty Gulch, 

 Crested Butte Co., Colorado, at an 

 altitude of 12,000 feet, on the i6th of 

 September, 1884. The snow-fall of 

 1883-4 ^^^ very unusual, proving a 

 great barrier to mining operations in 

 this district. In the spring of 1884 

 tbe uplands and valleys that were 

 still covered with snow presented 

 (^uite a novel appearance, the red and 

 white blended together in beautiful 

 harmony. What it was or whence 

 it came was quite a mystery to the 

 miners, and in hopes that you will 

 elucidate the mystery I take the 

 liberty of sending you a small quantity. 



' The snow-ball that yielded this 

 sediment was gathered from snow 

 that was about six feet in depth. It 

 changed its color to brown, but by 

 wetting a few grains and rubbing on 

 white paper it is red.' 



I made a few observations on this 

 specimen, and attempted to cultivate 

 some of the cells, but without success. 

 The cells were of a bright red color, 

 sometimes apparently quite naked, 

 but frequently enclosed singly, or 

 three or more together, in a colorless, 

 shrivelled envelope. The cells, ex- 

 clusive of the outer envelope, meas- 

 ured from 14.3// to 29.2,'/ in diameter. 

 Occasionally small naked cells were 

 observed only 6.5/7. in diameter. 



The contents of perfect and fresh 

 cells appears to be quite clear and 

 transparent, with occasionally a well- 

 defined sort of vesicle of a deeper 

 color than the rest. 



When the endochrome was pressed 

 out from the cells into the surround- 

 ing water, it contracted in spherical, 

 oil-like masses. 



The surrounding envelope is quite 

 hard, tough, and resisting. 

 o 



Photo-Mjcrograpliy. — II. 



BY THE EDITOR. 



2. Apparatus. 



We have deemed it advisable to 

 reverse the intended order of the sub- 

 heads of this division of the subject, 

 that we may have opportunity to test 

 a form of apparatus w^hich we desire 

 to describe in this connection should 

 it prove satisfactory. W^e will there- 

 fore defer the description of micro- 

 scope and camera until next month, 

 taking up now 



a. Plates^ Chemicals., Devel- 

 opi7tg Apparatus^ Darh- 

 room, etc. 



Plates. — It is not our province to 

 advocate the use of any particular 

 band of plates, since all the large 

 manufacturers doubtless furnish good 

 plates. The kind best adapted to 

 photo-micrography is a moderately 

 quick plate that works clear. A plate 

 that yields a negative covered with a 

 general fog, such as some of the more 

 rapid ones are apt to show, is not to 

 be recommended. It must not be 

 inferred, ' however, that extremely 

 rapid plates cannot be found that 

 work perfectly clear. Some makers, 

 in attempting to excel in the sensi- 

 tiveness of their emulsions, go so far 

 that a very slight forcing in the de- 

 velopment causes a noticeable gen- 

 eral fog over the plates. The advan- 

 tage of extreme rapidity obtained at 

 the expense of clearness in the shad- 

 ows, is, to say the least, questionable. 

 So long as the plate works clear, its 

 rapidity is a secondary consideration. 

 Doubtless a moderately rapid plate 

 will be most generally preferred for 

 work with powers up to a ^-inch, 

 and quicker plates for higher powers. 



Developing Apparatus. — The ne- 

 cessary apparatus, which should be 

 purchased at the beginning, is the 

 same as would be required for field 

 work. We give a list of the articles, 

 witli the current prices appended : — 



