1905.] NATURAL SCIENCES OF PHILADELPHIA. 563 



It has seemed to Mr. Tilghman and to me to be better for us each to 

 discuss this matter from our separate points of view — he from the point 

 of view of a physicist, chemist and mathematician, and I from the 

 point of view of a geologist. 



The number of arguments which between us we have worked out, 

 in support of the theory that this gigantic hole is an impact crater, will 

 be set forth in the two following papers. It must be remembered that 

 while a great deal of the evidence collected by us is positively in favor 

 of the theory, much of it is negatively so; that is to say it disproves the 

 theory that this great hole is the crater of an ancient volcano, or was 

 produced by an explosion of steam, which latter theory seems to have 

 been adopted by Mr. G. K. Gilbert on what seems to be very insufficient 

 evidence. Perhaps it would be more accurate and just to say that he 

 has adopted this theory because of an inadequate examination of the 

 phenomena at Coon IMountain, or, as it is frequently called, Coon Butte ; 

 for had he examined the surface carefully, it does not seem possible to 

 me that any experienced geo'ogist could have arrived at such a con- 

 clusion. 



Coon Mountain and Its Crater, 



There is to be found in the almost level plain country, about five miles 

 almost due south of Sunshine Station, on the Atchison, Topeka & Santa 



The result represented 3.63 grammes platinum and 14.96 grammes iridium 

 per ton (of 2,000 lbs.) of the original meteoric iron, with probably a trace of 

 rhodium 



I add the following remarks : 



1. Mr. Alexander in using his method undoubtedly dissolved out with aqua 

 regia from his cupelled button not only gold and platinum but some iridium, 

 so that the loss of weight (after deduction of gold added) represented not merely 

 platinum, as he assumed, l3ut in part iridium also. 



2. On tlie other hand, it is not certain that in my process all the iridium is 

 dissolved out from the original material (residue sent me by Mr. Alexander) by 

 aqua regia as used. 



3. My results as to separation of the two platinoid metals are fairly trust- 

 worthy, but would be more so if there had been a larger absolute quantity of 

 material to work on. 



4. It is of course possible that these platinoid metals are not uniformly .dis- 

 tributed in the original meteoric iron. 



Believe me. 



Sincerely yours, 



(Signed) J. W. Mallet. 



From the specimen of Caiion Diablo iron you left for me, with drill holes in it 

 and a memorandum as to drills being blunted and spoiled, I have obtained five 

 excellent microscopic diamonds — quite like those of South Africa in appearance 

 and markings. 



J. W. M. 



