260 



single key in the door of a wardrobe, was set in motion, so as to pro- 

 duce a distinct rattling. A similar rattling of the keys was noticed 

 by the invalid alluded to, two or three times in the night, between 

 3 and 5 o'clock, A. M., as nearly as recollected, when there was no 

 one moving in the house. 



Dr. Patterson, recurring to some of the views taken by Prof. 

 Rogers, expressed a doubt whether the phenomenon of the 

 earthquake may not be more properly regarded as a motion 

 of the earth's crust, imparted to it directly from the originating 

 cause, without necessary reference to the movement of the fluid 

 beneath; and he compared it to the vibrations of sounding bo- 

 dies, whether transverse or longitudinal. 



Further remarks were made by Prof. Rogers, Prof. Frazer, 

 and Mr. G. W. Smith, on the same subject. 



Major Graham described a Reflecting Lantern and a Helio- 

 trope, used by him as meridian marks for great distances, in 

 1841, while tracing, in his capacity of U. S. Commissioner, the 

 due North line from the monument at the source of the River 

 St. Croix. 



The lantern was constructed by Messrs. Henry N. Hooper & Co., 

 of Boston, under Major G.'s directions. It was similar in form to the 

 Parabolic Reflector Lantern, sometimes used in lighthouses, but much 

 smaller, so as to be portable. 



The burner was of the Argand character, with a cylindrical wick, 

 whose transverse section was half an inch in diameter, supplied with 

 oil in the ordinary manner. This was placed in the focus of a para- 

 bolic reflector, or paraboloid of sheet copper, lined inside with silver 

 about one-twentieth of an inch in thickness, polished very smooth 

 and bright. The dimensions were as follows : — 



Inches. 

 Diameter of the base of frustrum of reflector, - - 16. 



Distance of vertex from base, - - - - - 3.75 



Distance of focus from vertex, ..... 2.25 



Diameter of cylindrical burner, - - - - .50 



Diameter of a larger burner, which was never used, but 



which by an adapting piece could be easily substituted, 1.25 



The instrument answered the purpose for which it was intended, 

 admirably well, and was of great use in tracing the due north line. 

 While it occupied the station at Park's Hill, 15 feet above the surface 

 of the ground, or 828 feet above the sea, in the latter part of Septem- 



