lxiv Trans. Acad. Set. of St. Louis. 



President Edmund A. Engler. 



First Vice-President D. S. H. Smith. 



Second Vice-President M. H. Post. 



Recording Secretary William Trelease. 



Corresponding Secretary Hermann von Schrenk. 



Treasurer Enno Sander. 



Librarian G. Hambach. 



Curators G. Hambach, 



Julius Hurter, 

 Robert J. Terry. 



Directors H. W. Eliot, 



Adolph Herthel. 



A paper by Mr. F. C. Baker, entitled A revision of the 

 Limnaeas of northern Illinois, was presented and read by 

 title. 



Dr. O. Widmaun read an interesting account of the great 

 St. Louis crow- roost, in which were embodied many facts 

 concerning the life-history and habits of the common crow. 



Professor F. E. Nipher gave an account of some of his 

 recent results in positive photography. He has now found 

 that hydrochinone baths of normal strength may be used. 

 The formula given in each box of Cramer plates yields good 

 results, if the mixed bath is diluted with water to one-third 

 strength. The potassium bromide may be left out, and one 

 drop of concentrated hypo solution must be added for each 

 ounce of diluted bath. The hypo has a most wonderful 

 effect. With the same bath, plates may be developed as 

 positives, in the dark room or in direct sunlight. He had 

 even started the developing of a plate in a dark room, where 

 it progressed very slowly, but very satisfactorily, continued 

 the operation in diffused daylight in an adjoining room, and 

 finished the operation in direct sunlight. The process was 

 accelerated by the light, but did not appear to be otherwise 

 changed by the change in illumination. The resulting pic- 

 ture could not be distinguished from those produced by ordi- 

 nary methods. This picture was shown by means of the 

 lantern. 



A box of Cramer's "Crown," "Banner" or " Isochro- 

 matic " plates may have the plates individually wrapped in 

 black paper, in the dark room or at night, and all the re- 

 maining work may be done in the light. A plate is taken 



