134 



THE AMERICAN MONTHLY 



[July, 



transmission of a greater amount of 

 light than is obtainable by the polari- 

 scope, renders objects thus seen 

 much more effective. It is con- 

 structed as follows : — Into the tube 

 of the spot-lens a short tube is made 

 to move freely and easily. This in- 

 ner tube has a dovible flange, the outer 

 one (which is milled) for rotating, 

 and the inner one for carrying a glass 

 plate. This plate is made of flat, 

 clear glass, and upon it are cemented 

 by a very small quantity ot l^alsam 

 three pieces of colored (stained) 

 glass, blue, red, and green, in the 

 proportion of about 8,5, and 3 . The 

 light trom the lamp is allowed to pass 

 to some extent through the inter- 

 spaces, and is by comparison a strong 

 yellow, thus giving four principal 

 colors. Secondary colors are formed 

 by a combination of the rays in pass- 

 ing through the spot-lens. 



' The stained glass should be as rich 

 in color and as good in quality as pos- 

 sible, and a better eflect is obtained 

 by three pieces of stained glass than 

 by a number of small pieces. The 

 application of the chromatoscope is 

 almost unlimited, as it can be used 

 with all objectives up to the ^. Trans- 

 parent objects, particularly crystals 

 which will not polarize, diatoms, in- 

 fusoria, palates of molluscs, etc., can 

 not only be seen to greater advantage, 

 but their parts can be more easily 

 studied. As its cost is merely nomi- 

 nal, it can be applied to every instru- 

 ment, large or small, and when its 

 merits and its utility by practice are 

 known, I am confident that it will be 

 considered a valuable accessory to 

 the microscope.' 



— Prof. W. O. Atwatcr, as the results 

 of a series of experiments, finds, contrary 

 to the general opinion of chemists, that 

 plants assimilate nitrogen from the atmos- 

 phere. They take up the greatest quan- 

 tity when supplied with ahundant nourish- 

 ment from the soil. Well-fed plants ac- 

 quired fully one-half their total nitrogen 

 from the air. It seems probable that the 

 free nitrogen of the air is in some way 

 assimilated by the plants. 



EDITORIAL. 



Publisher's Notices.— All communications, re- 

 mittances, exchanges, etc., should be addressed to the 

 Ldiior, P. O. Box 630, Washington, D C. 



Remittances should be made by postal notes, money 

 orders, or by money sent in registered letters. Drafts 

 should be made payable in Washington, New York, 

 Boston, or Philadelphia. 



Subscription-price before April ist, ;Jii per year, in 

 advance. All subscriptions begin with the January 

 number. After April tst the subscription-price will 

 be gi.50. 



The regular receipt of the Jodrnal, which is issued 

 on the 15th of each month, will be an acknowledgment 

 of payment. 



'I he first volume, 1880, is entirely out of print The 

 succeeding volumes will be sent by the publisher for 

 the prices given bflow, which are net. 



Vol. 11 (1881) complete, $1 50, 



Vol III (1882) complete, $2 00. 



Vol. IV (1883) complete, J1.50. 



Vol. V (1884) complete, Ji.so. 



Vol. V (1884), Nos. 2-12, $1.00. 



Scientific Meetings. — The A. 

 A. A. S. meets this year at Ann 

 Arbor, Mich., on the 26th of Au- 

 gust. A large attendance is antici- 

 pated and plans for the meeting are 

 well advanced, calculated to make an 

 interesting one. 



The American Society of Micro- 

 scopists meets at Cleveland, where 

 great preparations are under way for 

 the occasion. A circular concerning 

 this meeting will be found inserted 

 in this number of the Journal. 

 Press of matter this month forbids 

 further notice of either of these meet- 



The Postal Club. — A few weeks 

 ago Dr. Ward gave us a short but 

 thoroughly satisfactory account of the 

 condition of the Postal Microscopical 

 Club. He said the afl'airs of the 

 club were being closed up for the year, 

 ' with every vow fulfilled,' ' all the 

 circuits being now upon the last box 

 of the number assigned when we 

 started last fall.' No other boxes 

 will be sent out until September. 



We can understand the satisfaction 

 the officers of the Club must feel at 

 such a result. It has only been se- 

 cured by having a careful system 

 whereby the course of every box can 

 be followed throughout its migrations, 

 and wherever there is delay the cause 

 can be promptly discovered and re- 

 moved. Eflicient management in ad- 



