HISTORY OF GEOLOGICAL SURVEY. 4! 



found chrysolite in Skye, according to his two articles in Vols. Ill and IV of the Trans- 

 actions of the Geological Society of London, only in trap or "amygdaloid;" and he 

 repeats the same essentially in his work on rocks, the chrysolite being spoken of as 

 occurring in an eruptive or overlying rock. Greg and Lettsom, in their work on British 

 Mineralogy (1858), confirm this by speaking of the chrysolite of Skye as being found 

 in trap. Moreover, the chrysolite is one of three constituents, the other two being 

 hornblende or augite, and a feldspar ; and the rock is not Laurentian or Norian. 



The rock of Elfdalen is undoubtedly related to that of Waterville, and yet is widely 

 different. I have not seen Rose's description of it. But Senft, to whom Mr. Hunt 

 refers, speaks of it as a hypersthene rock, that is, a granular compound of labradorite 

 and hypersthene, with grains of chrysolite as an accessory ingredient. The ossipyte, 

 on the contrary, consists almost solely of labradorite and chrysolite, there being "only 

 a very little of a black mineral, probably hornblende." I examined the specimens of 

 ossipyte with Mr. Dana, the same that I collected when in Waterville with you, and 

 through much of it could detect no hornblende whatever. Mr. Dana was right, there- 

 fore, in saying that this Waterville rock, consisting essentially of labradorite and 

 chrysolite, is one not previously described. The principal constituent, besides the two 

 mentioned, was the titaniferous iron ore, which he found distributed in microscopic 

 grains through the labradorite. 



The light colored rock, from a point higher up the stream, determined to be a 

 labradorite rock by Mr. Dana, is, as he observes, wholly different from the ossipyte, it 

 containing much hornblende and no chrysolite ; and the titaniferous iron ore in visible 

 grains, instead of invisible particles disseminated through the labradorite. 



After the publication of these letters, Dr. Hunt writes to the effect that 

 he had personally examined Macculloch's specimens in Europe, and felt 

 confident that the rock of Skye was the same with that from Waterville. 

 Per contra, Prof. Dana communicates a message from Prof. Geikie, direc- 

 tor of the geological survey of Scotland, in which it is stated that the 

 rock of Skye is an eruptive rock related to trap. Whatever may be the 

 truth as to the Scottish rock, it is clear that no one had proposed any 

 technical name for this mineral aggregate before Mr. Dana; and there- 

 fore, by the canons of lithological nomenclature, the designation of 

 "ossipyte" is entitled to recognition and acceptance. 



The 1871 report contains a full description of this locality at Water- 

 ville, and an enumeration of the other localities of the same formation. 

 These are Sabba Day and Down's brooks, Waterville ; Loon pond, Wood- 

 stock; Lafayette range; Mt. Tom; Mt. Washington river; and Sable 

 mountain, in Jackson. These are the only ones in which the mineral 

 labradorite had been found in the area of the map. 

 VOL. i. 6 



