JOURNAL OF PROCEEDINGS. 227 



veiy much more excessive there than they are here, though the mean 

 temperature for January last is aearly the same, thus : 



Mean temp. Jan., 1863, at St. Louis, 37.4° At Denver, 

 at 7 A.M. " 33.1 



at 2 P.M. " 41.8 



at 9 P.M. " 37.1 



Therefore, the mean temperature of night and morning is much lower 

 there than here, and that of the middle of the day is much higher ; the 

 difference of the extremes being on an average 8.7° here, and 25.1° at 

 Denver. What the difference is in other months of the year, and what 

 the mean difference of the whole year, further observations must devel- 

 ope. The few results published by the Smithsonian Institution as ob- 

 tained by Mr. D. O. Collier at the same place, in the year 1859, fully bear 

 out the above propositions as far as they go. 



The second interesting feature of the climatic changes at the foot of the 

 Eocky Mountains, which, indeed had already been indicated by Dr. Par- 

 ry's observations of last summer, was the lesser fluctuations of the mean 

 atmospheric pressure and mean temperature there, compared with the 

 same at St. Louis. In the diagram (which was here exhibited) our curve 

 was found to be much more wavy, the atmospheric ocean more stormy, 

 than that representing the similar data at Denver. The diagram eluci- 

 dated a third very important feature, in this, that the atmospheric changes 

 at Denver occurred invariably one, often two, and rarely three days in 

 advance of ours ; just as they generally take place, one or one and a half 

 days sooner here than on the Atlantic coast. This is true in regard to 

 barometrical as well as thermometrical changes. In thirty-one days of 

 the month, I have noted seven rises of the mean daily temperature and 

 seven falls, at Denver, corresponding with similar changes here. Some- 

 times the changes were greater at Denver, but usually they are more 

 marked here. Dr. Parry's observations of last summer indicate (as stated 

 on a former occasion) a different law. His results make the changes often 

 simultaneous, and not rarely a day later, in the Rocky Mountains than 

 here, and only in a very few instances earlier ; so that, if we may venture 

 to draw deductions from the very limited number of observations at our 

 disposal, we may come to the conclusion, that, in winter, the atmospheric 

 changes in the Rocky Mountains, or at their base, precede those in the 

 Mississippi Valley, and that in summer they are simultaneous or even 

 earlier there than here. The facts being once established, the causes re- 

 main to be ascertained. 



Mr. Broadhead presented some fossils from the Hudson 

 River Group of Ohio. 



April 20, 1863. 

 The President, Dr. Exgelmaxx, in the chair. 



Letters were read from the Smithsonian Institution, April 

 2, 1863, concerning the transmission of exchanges, and from 

 the Konigl. Bayerische Akad. des Wissenschaften, Munich, 

 Nov. 6, 18G2, announcing publications sent. 



The Corresponding Secretary laid upon the table the Jour. 

 of the Acad, of Nat. Sciences, Philadelphia, Vol. V., Part iii., 

 from the Academy. 



