738 KANSAS CITY REVIEW OF SCIENCE. 



In the northeast part of Reynolds County and northern part of Madison 

 County eruptive porphyry has been found of a gray color and containing large 

 crystals of white feldspar. 



Near Polks' in Iron County are found amygdaloidal rocks flanked with por- 

 phyry. The Amygdules are of a white mineral. A few miles southward the 

 porphyry contains blue crystals. 



■ There is a good exhibition of a dolerite dyke in porphyry on Mine La Motte 

 property at the Jack diggings. Another dyke is at a cave on Rock Creek. 



The porphyries are generally very hard and difficult to work, so it is not prob- 

 able that they will be used very soon except for paving purposes. The porphy- 

 ries are of course very difficult to polish on account of their hardness, and neces- 

 sarily will be expensive to polish; still in the future some of us may expect to see 

 polished columns of Missouri porphyry. 



There were on exhibition at the Centennial Exhibition, Philadelphia, several 

 fine exhibits of porphyry polished columns; one inlaid table of red porphyry was 

 valued at $7,500. This was from Elfdalen, in Dalecarlier, Sweden. It was of a 

 dark red color and very much resembled some Missouri porphyrites. Similar 

 porphyry is also found in eastern Massachusetts. 



Having closely examined certain porphyries of Massachusetts, New Bruns- 

 wick and Wisconsin, I find them all to resemble ours of Missouri. If specimens 

 from these different localities were thrown together with a lot of Missouri speci- 

 mens of porphyry, one at a glance would be inclined to say they were all from 

 the same place. Dr. T. Sterry Hunt at various times has assigned these to the 

 age of the Huronian, T, B. Book also assigns those of Lake Superior to same 

 age. I thus am inclined to believe our porphyries to be of Huronian age. The 

 granites may be older, they may be Laurentian. The trap dykes of dolerite, etc., 

 are of an age more recent than either the granites or porphyries, and are proba- 

 bly of synchronous age. They are intrusive in both the granite and porphyries. 



THE VALUE OF OUR COAL ANNUALLY. 



The coal production of the United States for the year 1881, is estimated by 

 competent judges to amount to seventy miUions of tons, and counting the cost of 

 mining and preparation for market, royalty or ground rent, and, a reasonable 

 profit for the miner, as aggregating on an average $2 per ton, the output repre- 

 senting an actual value at the pit's mouth of one hundred and forty millions of dol- 

 lars. The cost of transportation to market may be counted at an average of one 

 and a half cents per ton per mile, which, for an average haul of 150 miles, would 

 make say one hundred and fifty-seven millions of dollars for the whole amount 

 delivered to consumers. Adding to this the expense of marketing, commissions, 

 interest, etc., which may be placed at fifty cents per ton, and we have the actual 

 cost of our seventy million tons of coal to consumers as nearly three hundred 

 and thirty-two millions of dollars. From the mean value of about $4.75, the cost 



