Proceedings . 1 7 



the fact that cholera has already made its appearance and that it usually 

 continues its ravages for several years it can be expected to make its ap- 

 pearance the coming year, especially if the weather be moist and w^arm. 

 Knowing that cholera follows the routes of commerce and knowing that 

 there will be an enormous increase of traffic and immigration on account of 

 the Columbian World's Fair in Chicago, a cholera epidemic is therebj^ much 

 more liable to occur. The cities near the St. Lawrence river, the great 

 lakes, the Atlantic and Gulf of Mexico will be particularly exposed. 



The writer does not attach any special importance to arresting immi- 

 gration unless all commercial intercourse were also stopped and that would 

 be more harmful than the epidemic itself. The plan suggested is to appoint 

 thoroughly qualified national health officers with police authority to look 

 after the sanitary conditions of every city in the Union. This vshould begin 

 now and not after the cholera has made its appearance. Cholera can be 

 easily prevented if proper precautions are taken, and even after it has made 

 its appearance it is easily controlled under proper treatment. 



A map accompanied the paper showing the probable routes and distri- 

 bution of cholera in 1893. 



This paper was discussed by Dr. E. S. Kellej^ health offi- 

 cer of Minneapolis, and others. 



The Saint Peter sandstone by F. W. Sardeson. [See 

 Paper D.] 



The Rum river valley as a botanical district, by E. P. 

 Sheldon; read for the author, bv C. A. Ballard. [See paper 

 E.] 



December 6, 1892. 



Twenty persons were present. 

 Corresponding Secretary W. H. Pratt, presided. 

 The following program was carried out: 

 A review of some points in the history of microscopy, by 

 Chas. P. Berkey. 



The subject w^as treated for the most part historically. The object w^as 

 to note the early inventions of lenses, and to trace the various subsequent 

 important improvements in both simple magnifiers and in combinations 

 up to the early part of the present century. A chart was used to illustrate 

 the appearance and adjustment of Leeuwenhoek's simple microscopes. In 

 conclusion the paper outlined some of the late improvements and called at- 

 tention to the broadened usefulness of the instrument in the last fifty years. 



The use of the microscope in the study of the plant lice. 

 — O. W. Oestlund. 



[abstract.] 

 Attention was called to the insufficiency of the characters generally used 

 by entomologists for the distinction of species of the aphididae as the number 



