Association of American Geologists and Naturalists. 145 



2. In the aggregation of molecules by attraction, only equal or 

 homologous axes unite. 



3. The axes of cohesive attraction in molecules have opposite 

 polarity at opposite extremities — that is, the opposite poles are 

 positive and negative, or north and south, as the terms are ordina- 

 rily used. 



4. The polarity of the molecules may be reversed by extrinsic 

 influences. 



5. The axes and polarity of cohesive attraction in solidification 

 exist before the union of the molecules, instead of being a conse- 

 quence of that union. 



6. The axial lines of cohesive attraction are not indefinitely fixed 

 in position, but in some way modified in direction and force by tem- 

 perature. 



7. The variations which the attraction of cohesion undergoes, 

 take place according to some simple ratio. 



8. The homologous parts of molecules similarly and simultane- 

 ously undei'go this variation as regards the attraction. 



9. In some cases the parts of a molecule or opposite sides of a 

 pole, undergo a different amount of variation. This takes place 

 symmetrically with regard to all the poles. 



10. If the state of attraction which produces a primary cube or 

 prism is considered in its normal state, when secondary planes are 

 produced, there is a decrease of force in the direction of the prin- 

 cipal axis, and this decrease is in some simple ratio. 



11. The diminution of attracting force in the primary axis, on 

 which the formation of a secondary depends, consists in the partial 

 action of their force along intermediate axes synnnetrically situated 

 with reference to primai'y axes ; and the greater or less amount of 

 diminution determines the kind of distribution. 



12. Tlie direction of cleavage may indicate in any species of mat- 

 ter which set of axes is dominant or strongest in attracting force, 

 the primary or secondary set. 



13. Those variations of attraction producing secondary forms, de- 

 pend often on surrounding bodies favouring the concentration or dif- 

 fusion of the attracting force, and causes often act simultaneously in 

 nature over wide areas. 



14. In an enlarging crystal one axis (or two) may have the ac- 

 tion of attraction accelerated by extrinsic influence, and this accele- 

 ration or retardation affects equally all crystals forming together 

 under the common circumstances. 



15. The action of cohesive attraction is often intermitted, pro- 

 ducing seriate results, as exemplified in the cleavage of crystals, and 

 the specific rate of intermittent action is different for unequal axis. 



A letter was received from President Everett, inviting the Asso- 

 ciation to hold its next annual meeting at the University in Cam- 

 bridge. The invitation was declined for the coming year, and on 



VOL. XlilV. XO. lA.KW'II. — JAX. 1848. IC 



