26 J. C. Branner — Hydrocarbon Found in Brazil. 



Professor F. J. Rogers of the Physics Department of Stan- 

 ford University kindly tested the conductivity of this material, 

 but, owing to the small size of the fragments and to its fria- 

 bility, no absolute measure of its conductivity could be made. 

 The general conclusion was reached, however, that it has a low 

 conductivity, about like that of bituminous coal. As an insu- 

 lator it is not as good as elaterite, Cuban asphaltum, or alber- 

 tite. 



When I first heard of this hydrocarbon I thought it possible 

 that it might be genetically related to the diamonds and car- 

 bonados of the region in which it was found. But the size 

 and occurrence of these lumps in recent gravels do not bear 

 out such a theory. 



Attempts to obtain specimens of this material from other 

 localities disclosed the fact that the term "gelo" is also applied 

 to material other than hydrocarbon. For example, Mr. Arthur 

 R. Turney of Cachorros has sent me several specimens of what 

 is called "gelo" at the diamond washings at Mosquitos, a few 

 miles south of the city of Lencoes. The materials from near 

 Lencoes, however, are simply hard beds of various thicknesses 

 in the recent gravels. They are made up of sands and water- 

 worn pebbles firmly cemented. They contain no lime and 

 very little iron, and it is therefore inferred that the cementing 

 matter is silica. 



Stanford University, California. 



