AUGUST 19, 1921 WATSON: LAMPROPHYRE DIKE 341 



the working together of entomologists, of pathologists and of chemists. 

 The entomologist indeed has a twofold task. Not merely must he 

 test out the substances created by the chemist, but he must also create 

 the science of the pharmacology of insects. 



Some desultory work of this type has been done in the past. The 

 Bureau of Entomology of the U. S. Department of Agriculture from 

 time to time has tested out numerous substances, often by-products 

 for which no other use was apparent, such substances as naphthols, 

 cresols, crude pyridin bases and many others. These were all found 

 to be comparatively worthless for one cause or another. Few if 

 any systematic studies in which the chemist and the entomologist 

 cooperated seem to have been made. Such studies are now in progress 

 through the cooperation of the Bureau of Entomology and of the 

 Bureau of Chemistry. Notable progress has been made and it is 

 hoped that a solid foundation will be laid for a new science — chemo- 

 phyto-therapy. 



My hope in addressing you was to give you a conception of the 

 pharmacologist which is perhaps not generally current and to indicate 

 to you how fundamental are some of the problems with which he deals. 

 If I have succeeded in arousing your interest in this science and if 

 in so doing I have demonstrated to you that the action of chemical 

 substances upon living things is quite as much a function of the physi- 

 cal properties of such substances as it is of their molecular structure, 

 then I have achieved the goal that I set for myself this evening. 



PETROLOGY. — Petrography of a lamprophyre dike cutting a pyrite 

 body in Boyd Smith Mine, Louisa County, Virginia.'^ Thomas 

 L. Watson, University of Virginia. 



The important large lens-shaped bodies of pyrite in Louisa County, 

 Virginia, so vigorously worked for many years, are inclosed in schists 

 of probable Cambrian age. These pyrite bodies, as well as the more 

 or less closely associated gold deposits, are genetically related to 

 intrusions of plutonic igneous rocks which are exposed in large masses 

 in fairly close proximity to the ore bodies. The ore-bearing schists 

 are also intruded in places by dikes of both acidic and basic igneous 

 rocks, the latest of which is diabase of Triassic age. 



Although the area is one in which igneous rocks, in part younger 

 than the ore bodies, are fairly common, and in which mining operations 

 have been in progress for a long period of years, not until recently 



1 Received June 16, 1921. 



