318 On the Light-House System of ithe United States. 
23d. The velocity of transmission of mercury through tin is 
at first slower than that through lead, but it differs in being uni- 
form, while the velocity in lead rapidly diminishes. 
. The syphon action in atin bar cannot be long main- 
tained on account of the crystallization and consequent brittle- 
ness of the bar. 
25th. The crystalline amalgam has a constitution of Hg Sn,. 
26th. The liquid amalgam contains 
55 per cent. of tin to 98-45 per cent. of mercury. 
27th. The crystalline amalgam loses nothing by atmospheric 
diffusion. 
- 28th. Quicksilver permeates gold and silver but very slowly. 
29th. Zine and cadmium are permeable to mercury, but dis- 
solve in it. 
30th. Tron, platinum, palladium, copper and brass, are, at com- 
mon temperature, not permeable to mercury. 
Note.—I am indebted for ‘most of the foregoing analyses to 
Messrs. Homer, Hague, Dwight, Worcester, Mariner, and Dean, 
pupils in my laboratory, who have kindly codperated with me in 
promoting the research. 
Arr. XXVIIL—E tract from the Report of the Board of Offi- 
cers convened under the direction of Hon. Thomas Corwin, 
Secretary of the Treasury, on the Light House System of the 
United States coast.* 
Str: The light-house board have the honor to submit the re- 
port of their investigations, and the conclusions they have arriv- 
ed at, under your instructions of the 2ist May, 1851, hereto ap- 
pended, in conformity to the 8th section of the act making ap- 
propriations for light-houses, light-boats, buoys, é&c., approved 
March 3, 1851, in the following words : 
“ And be it further enacted, ‘That the Secretary of the Treas- 
ury be, and is hereby, authorized and required to cause a boar 
to be convened at as early a day as may be practicable after the 
passage of this act, to be composed of two officers of the Navy 
of high rank, two officers of engineers of the Army, and such 
civil officer of high scientific attainments as may be under the 
orders or at the disposition of the Treasury Department, and a 
AR RE 
* The at im i j ; 
pubes UE shove site fom Shit Regtee Ohana ee tamed tote, 
originates, consisted of Commodore Wm. B. Shubrick, U.S. Navy, ‘Commander S. 
F, Du Pont, U. 8. Navy, Brevet Brigadier General G. Totten, U.S. of 
Engineers, ‘Lieut. Col. James Kearney, U.S. To ieal ‘3, Prof. A. D. 
Bache. LLD., Superintendent Coast Survey, Lieut. he al A. ve, U.S. Navy, 
Secretary. 
