1867.J 315 [Ilayden. 



2. The influence of the winds is most marked in the Ni)rthern 

 and Western hemispheres; that of solar obliquity in the Southern 

 and Eastern hemispheres. 



3. Where the sun's rays are least intense (as in the l^)lar Kegions), 

 and whore the winds are most variable, the ratios exhibit the nearest 

 parallelism to the increments of arc; but where the winds are most 

 unifurm (in and near the region of monsoons) they correspond more 

 closely with the sinal increments. 



4. The general changes of temperature at midwinter, and at the 

 equinoctial seasons (when the sun's declination is changing most 

 rapidly), are most dependent upon the local solar heat; the mid- 

 summer changes are more subject to the influence of the winds. 



5. The greatest conflict of opposing forces occurs during the sun's 

 passage between the comparatively wind-governed Northern hemis- 

 phere and the sun-governed Southern hemisphere. The conflict is 

 manifested in the spring and autumn rains. 



6. The closest and most general approximation of ratios is shown 

 in the monthly temperature-change at midsummer, which (in the II. 

 mean), corresponds precisely with the change of arc. 



Dr. Ilayden spoke of the geographical distribution of 

 plants, and referred to a number of species which are con- 

 sidered as exotics in this part of our country, but indigenous 

 in regions west of the Mississippi. 



Dr. Hayden said that the reading of a remarkable volume, recently 

 published in England, had suggested some remarks in regard to the 

 geographical distribution of the Flora and Fauna of the country west 

 of the Mississippi. The book referred to is entitled the " Geographi- 

 cal Distribution of Mammals," by Andrew Murray. He had noticed 

 a few plants in the Valley of the Missouri, which are undoubtedly 

 indigenous there, but they have always been, and are regarded now 

 as introduced east of the Mississippi. 



1. Portulacca ohracea : Nuttall, in his genera of North Ameri- 

 can plants, says, "Indigenous on the saline and denudated plains of 

 the Missouri, a plant common to every part of the globe." Gray, 

 "Common in cultivated and waste grounds, naturalized from Eu- 

 rope." Dr. Darlington, " Undoubtedly an introduced plant here." 

 Dr. Gray, in one of his later works, says, it is undoubtedly wild in 

 Arkansas and Texas. Dr. Torrey says, that in the Atlantic States it 



