174 



THE GUIDE T< > NATURE 



Dakota. They are hardly ever larger 

 than a hen's egg, and the interior is 

 lined with beautiful, frost-like, drusy 

 quartz, while sometimes loose, doubly 

 terminated crystals of quartz or caleite 

 are found in them. 



I have one in which plates of trans- 

 parent selenite nearly fill the cavity. 

 At Ballast Point, near Tampa, Florida, 

 geodes of chalcedony have been found 

 having the form and outward appear- 

 ance of coral. These are pseudo- 

 morphs by replacement, and some of 

 them are remarkably beautiful. 



In certain limestone formations of 

 Illinois, Missouri and Iowa, geodes are 

 plentiful and range in size from one 

 inch to a foot or more in diameter. 

 The "Keokuk beds," as they are called, 

 afford great quantities. 



Inside the shell of quartz or chalced- 

 ony, other materials are frequently 

 found, caleite, dolomite, selenite, pyrite 

 and sphalerite being the most common, 



while millerite in delicate, hair-like 

 crystallizations is occasionally met 

 with, and 1 have seen geodes that con- 

 tained asphaltum — no fairy grottos 

 these! 



At Bridgeport, Montgomery County, 

 Pennsylvania, I have collected geodes 

 of quartz that compare very favorably 

 with those from South Dakota. They 

 differ from those, however, in not hav- 

 ing a shell of chalcedony. 



Limonite commonly occurs in the 

 form of geodes, the interior surface 

 covered with a velvety coating of black 

 limonite, or the interior may present 

 mammillary or stalactitic forms, dull, 

 brilliant or iridescent as the case may 

 be. 



The study of geodes is an interesting 

 one, and the subject has been well 

 handled by Mr. Elmer Benge in a 

 series of articles published in "The 

 Mineral Collector," Vol. IV, to which 

 those interested are referred. 



< <<<<<<<<<<c<«cac««g<g<<cc«c«<«c«<c<<<<««c<c<ccc<<c<«^ 



'•••••••• • 



AGASSIZ ASSOCIATION' 



W<&<&&< &<<£8^^^^ 



Business Men and the AA. 



There is much of common sense, and 

 explanation of a puzzling situation, in 

 the following quotation from a letter 

 from an AA member : 



"Men of business training, not quite 

 familiar with the details of scientific 

 work in natural history, cannot be ex- 

 pected to adapt themselves to the fea- 

 tures of such an institution as The 

 Agassiz Association, any more than 

 the workers in such an association 

 would be able to conduct an organized 

 business, and yet both are of equal 

 importance. The Agassiz Association 

 is such a power for good in the educa- 

 tion of the people that very many bus- 

 iness men would be glad to back such 

 an institution heavily could they but 

 understand the effects of its working. 

 Mr. Carnegie has been particularly 



happy in his observation of instances 

 of this sort, and he has an instinct 

 which allows him to set useful men at 

 work without their being distracted by 

 the need for attention to financial mat- 

 ters." 



No organization for science and edu- 

 cation, and particularly of helpfulness 

 to young people, has ever accom- 

 plished so much as has the AA in its 

 thirty-five years of existence, with so 

 little money. The untiring, faithful, 

 self-sacrificing spirit of many of its 

 workers is convincing proof of what 

 could be done with reasonable finan- 

 cial support. It has always had a 

 superabundance of energy and a deficit 

 of money. What the organization 

 needs is a rating on what has been done, 

 and an appreciation of the possibilities 

 for the future. 



