732 Transactions of tee American Institute. 



meniscus lens was constructed to be placed in part of the objective, 

 shortening the focus about one-seventh, which was corrected by the aid 

 of the spectroscope, until the whole combination was perfectly cor- 

 rected for the actinic rays. 



Ikon Deposits est Alabama. 



Mr. Colton gave a description of the iron deposits in Alabama, and 

 exhibited specimens of the ore, and read the following paper: 



All the printed records one can find of the great mineral wealth 

 of Alabama consist of two small pamphlet reports by Prof. Tuomey, 

 and a few even smaller pamphlets of particular properties. I found 

 everywhere the greatest pride in the mineral wealth of the State, and 

 the most earnest desire for its development. The quantity of coal 

 consumed is now really very large, and the price fixed at a moderate 

 rate. 



Alabama has three coal fields — the Warrior, Cahawba and the 

 Coosa. The first and second I have visited ; the last is at present 

 inaccessible to transportation. The village of Montevalloo, on the 

 Selma, Rome and Dalton railroad, is the point from which I reached 

 the lower Cahawba field. This coal field has the shape of a pear with 

 one side partially cut out. It is located between the S. R. and 

 D. R. R. and Alabama and Chattanooga railroad, the large end being 

 south toward Selma, thence running northeast about thirty-six miles. 

 It contains about 300 square miles of coal lands, and supplied to the 

 Confederate navy yard and foundries at Selma and elsewhere, from 

 200 to 300 tons of coal per day for two or three years. Its northern 

 or northwestern edge is skirted by the A. & C. R. R. at a distance 

 „of two or three miles ; its southern is distant from the S. R. & D. R. R. 

 at Monte vallo and southward about two miles. The North and South 

 railroad runs through the northern neck. Montevallo is located just 

 where the chop-out or sunken portion commences. I visited the 

 openings near Montevallo, and then rode across the field and returned, 

 carefully examining the geological structure and outcrops. On the 

 south side the silurian rocks are pressed directly up to the coal, crowd- 

 ing out the sandstone and forcing the coal to a perpendicular, at some 

 points even to an incline southward. A section through this broad 

 part is represented on the blackboard, without indicating all the 

 veins. 



On the north side all is regular and in place, hence sixteen distinct 

 veins are to be traced. Many of these were opened during the war 

 and yielded quantities of excellent coal. In my exploration I was 



