RELATIONS TO OTHER SCIENCES 603 



place the relationship between these two branches in much detail, 

 just as it would be scarcely requisite to set forth the relationship 

 between paleontology and geology. 



Thus modern petrography stands to-day in the midst of a circle of 

 bordering sciences, and there is a mutual interchange of inspiration, 

 acknowledgment of indebtedness, and instruction. If our science 

 may not send to its neighbors the proud challenge Do ut des (I 

 give in order that thou mayest give), yet she does not promise too 

 much nor ask in vain when she makes the more modest request, Da 

 ut dem (Give thou to me and I also will then give something). 



