MUSEUM OF COMPARATIVE ZOOLOGY. 79 



a state of ignition." (L c, p. 490.) He states that the sandstones have 

 evidently been deposited in shoal water, on account of the abundant 

 ripple-marks occurring in them. 



Three species of fucoids, tolerably well defined, were said to have 

 been found in the red sandstone. The veins are considered to be of a 

 date posterior to the uplifting of the beds, and cut across all three of 

 the sedimentary rocks and the traps. They are taken as true veins, and 

 their mineral contents are said to change in the same vein as the rock 

 changes. The gangue is said to be principally quartz with occasional 

 calcite, and the ore to be most abundant at or near the junction of the 

 trap and conglomerate. He regards this district as being in its general 

 characters and in its veins like Cornwall. Conglomerates were noticed 

 with a cement of copper, but only in the immediate proximity to con- 

 siderable veins. He conceived the veins " to be veins of sublimation, 

 or in other words to be simply filled from below by the metal in a va- 

 porous state, and that all the compounds had their origin from copper 

 in a native form."* In 1843, he considered that the sandstone east of 

 Keweenaw Bay was older than the Trenton, while the western sand- 

 stones and conglomerates were formed during tlie period in which the 

 trap was upheaved, and were probably contemporaneous with the Xew 

 Red Sandstone. t 



It will be seen here that Dr. Houghton had entirely changed his 

 views regarding the relations of the sandstone. In 1841, the sandstone 

 of Keweenaw Point was said to be older than the St. Mary's sand- 

 stoiie ; in 1843, to be younger. 



Later, Dr. Houghton " said he could not speak definitely as to the 

 contemporaneousness" of this sandstone with that of Connecticut and 

 New Jersey, "but he was sure of the similarity of their structure." J 

 Prof. B. Silliman, Jr. at the same time stated that although he had 

 found the copper and silver from this region "fused into perfect union 

 at their two surfaces," they were not alloyed. § 



Prof. John Locke, in an article in 1844, || entitled "Observations 

 made in the Years 1838, '39, '40, '41, '42, and '43 to determine the Mag- 

 netical Dip and the Intensity of Magnetical Force, in several Parts of the 



* Am. Jour. Sci., 1841, (1,) XLT. 183-186; 1844, XLVII. 106. Trans, of the 

 Assoc, of Am. Geol. and Nat., 1840-1842, pp. 35-38. 

 t Am. Jour. Sri., 1843, (1,) XLV. 160. 



X Am. Jour. Sei., 1843, (1,) XbV. 332 ; 1844, XLVII. 107, 132. 

 § Am. Jour. Sci., 184-3, (1,) XLV. 332. 

 II Trans. Am. PhU. Soc, Phila., LX. 283-315, Apr. 19, 1844. 



