16 THE AMERICAN MONTHLY [January, 



has also a fine selection of old instruments, but both of them, like 

 Mr. Crisp, were unwilling to allow their treasures to be subjected 

 to the dangers of a long journey. The society will therefore be 

 compelled to fall back on the collection in the Army Medical Mu- 

 seum at Washington, which, it is hoped, the Government authori- 

 ties will bring here for exhibition. 



The exhibit of the society ought to be of a good deal of interest, 

 for in some senses it may be said that microscopy has reached its 

 acme. Prof. Abbe says that it is not probable that any glass will 

 be discovered of higher refractive index than that known, and with- 

 out that it is not possible to construct lenses of much higher power 

 or angle than at present. Our present objectives, then, are nearly 

 perfected, unless future investigations show our theory of light to 

 be erroneous. In regard to microscope stands, there are a large 

 number of forms for different purposes, many very attractive. 

 Klonne & Mueller, of Berlin, manufiicture one of the Zeiss form 

 wholly of aluminum, except the foot. Those who w^ill exhibit, 

 so far as they have already consented, are Baker, Swift, Crouch, 

 Beck & Beck, and Powell of London, Klonne & Mueller of Ber- 

 lin, Zeiss of Jena, Hartnack of Potsdam, Reichert of Vienna, 

 and probably Nachet of Paris, and Leitz of Wetzlar. 



One of the pleasant features of the exhibit will be that, by ex- 

 press permission of the manufacturers, the committee of the so- 

 ciety will be allowed to show the various stands and objectives 

 at the meetings of the society or at such times and places as may 

 be agreed on, so that all microscopists will have an opportunity of 

 seeing the best foreign work, and comparing it with that done in 

 this country. The domestic manufacturers will not be behind in 

 their display, and they have already taken the necessary steps to 

 be seen. Dr. E. Cutler, of New York city, has consented to 

 allow his famous Tolles 1-75 to be exhibited. The space assigned 

 to the society by Prof. Peabody, the chief of the department of 

 Liberal Arts, is in the south gallery of the Liberal Arts building, 

 next to the astronomical and photographic exhibits, and close to 

 the commercial displays of Bausch & Lomb, Queen & Co., Zeiss, 

 and others, and is in a very advantageous part of the building. 



Mosquitoes. — Petroleum has been found advantageous in pre- 

 venting the breeding of these insects. Four ounces in a pond 60 

 feet in area cleared it for 10 days. Creosote or any oil would 

 have the same effect probably. 



Mr. Howard, of the Agricultural Department, experimented 

 with kerosene upon a small area and killed 370 females. In 20 

 days these might have produced 74,000 young (200 each). It is 

 believed that this simple process of oiling the water of bogs and 

 ponds where they breed will greatly increase the value of lands 

 and of summer hotels near infested places. 



