Ixxvi 



both years a hot summer followed the cool May, but, of course, no predic- 

 tion can be based upon this fact. 



Dr. Engelmann also presented two diagrams showing the aver- 

 age temperature for each day of the month of January and May 

 for forty-seven years. The curves were much more irregular 

 than corresponding curves for London, adjacent days frequently 

 by two degrees. 



Mr. Nipher made a short communication regarding the deter- 

 mination of the constant for a galvanometer ; 



Some years since the question of the measurement of earth currents in 

 the Arctic regions came up, and it became desirable to know whether a 

 copper electrode used in determining the constant for the galvanometer 

 must be weighed soon, or whether with a reasonably strong current the 

 weighing might be deferred until the return of the expedition. With a 

 view of examining this point, a determination was made on February ist, 

 1880. The current ran for ih 317 m 30 s, depositing 0.3211 grammes of cop- 

 per. The electrode was then thrown loosely into the drawer of the bal- 

 ance, where it remained until April 4, 1882, when the same electrode was 

 found to have gained 0.0007 gramme in weight, showing thus no change 

 of importance in two years. 



yime 19, 1882. 



Dr. Engelmann, President, in the chair. Eleven members 

 present. 



G. W. Lettermann, of Allenton, presented specimens of the 

 wood of the Planera aquatica from Nevada Co., Ark.,, and of 

 the water-locust, Gleditschia monosperma^ from Newport, Ark. 

 He stated that 



both belong more especially to the flora of the southern States. The wa- 

 ter locust, however, makes its way up along the Mississippi river past St. 

 Louis, and Mr. H. Eggert found it about Alton, Ills., which seems to be 

 its northern limit. The Planera is a rarer tree, with very close grain. It 

 does not seem to occur north of the lowlands of south-east Missouri. As 

 they grow only in wet places, and rarely attain the size of a tree except in 

 deep swamps, both species are scarce in collections, and are not well 

 known even by woodmen in their native homes. 



Mr. Leonhard gave a description of the mineral formations of 

 Missouri. 



