2§ Geological Reports on the State of New York. 



which will exceed or come up to 5,000 feet, besides those now given in 

 the table." 



The heights of the mountains as given in this report, are sub- 

 stantially the same as those stated by Mr. Redfield, Vol. xxxiii, pp. 

 311 — 320 of this Journal. It appears that Mount Marcy, the high- 

 est mountain, is 5,467 feet above tide, or 267 feet above one mile. 

 Mount Mclntyre is 5,183 feet, Dix 5,200, and Dial mountain 

 4,900 ; thus four of these peaks differ little from one mile in ele- 

 vation, while Mount ¥/"ashington, in New Hampshire, is nearly 

 800 feet higher than Mount Marcy, and therefore maintains its 

 rank as the highest peak east of the Rocky Mountains.* 



"Variation of the Magnetic Needle. — This subject, not provided 

 for by the law of the State authorizmg the survey, has attracted 

 the attention of Mr. Emmons and his associate, Prof. Hopkins, 

 of Williams College, who makes the following remarks respecting 

 the influence of iron, particularly in this district : 



"The extensive iron deposits, which were noticed in the report of the 

 last year, constitute one of the most interesting features in the northern 

 geological section of the State. Considering the importance of these de- 

 posits in an economical point of view, nothing which may serve to throw 

 light upon their value or extent, can be regarded as irrelevant to the pur- 

 poses of this survey. In the present instance, there appears to be a mode 

 of establishing some general conclusions, at least, to which a clue could 

 not be furnished by those indications on which the geologist ordinarily 

 relies. This is to be found in the influence of large ferruginous masses 

 upon the magnetic needle. Deposits, far less extensive than those which 

 abound in Franklin county and Essex, are known to exert a local attrac- 

 tion, sufficient to derange the general directive tendency of the needle, 

 and render it entirely useless as an index to the true meridian. Nor 

 would it be at all surprising, even where no local derangement might be 

 apparent, should the needle be found to deviate some minutes, or even de- 

 grees, from the true magnetic north. Such a deviation, ascertained by 

 experiment at different points, might furnish a valuable criterion by which 

 to judge of the proximity of iron, of the direction of the bed or vein, and 

 perhaps its extent. This might especially be expected, were much of the 

 iron (as is the case in this district) of that kind known under the name of 

 the magnetic oxide." 



" The variation of the needle in this country at present is west, at all 

 points east of a certain line, called the line of no variation. This line 

 traverses the western and southern states, and appears itself not to be sta- 

 tionary. East of this line, the variation is increasing ; at least this is 



* This rank is now claimed for the Black fliountain, in North Carolina; height 

 6,476 feet. See this Journal, Vol. xxxv, p. 37U. 



