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of the base is exactly one kundred square inches. This cone or funnel 

 terminates in a tube Avhich carries the water into a receiving vessel. The 

 water which has fallen is measured by pouring it from the gauge into a 

 cylinder, so graduated as to indicate hundreths ot inches. A smaller 

 cylinder is also provided, v.diich gives thousanths of inches, and may 

 serve, in cases of accident, as a substitute for the larger cylinder. The- 

 rain gauge is placed in a cask sunk in the earth,, with its mouth near 

 the level of the ground. 



The snow gauge is a cylinder of zinc of the same diameter as the mouth 

 of the rain gauge. The measurement is made by pressing its moutk 

 downwards to the bottom of the snow, where it has fallen on a level 

 surface, then carefully inverting it, retaining the snow, by passing under 

 it a thin plate of metal. The snow is afterwards melted, and the water 

 produced is measured in one of the graduated glass cylinders of the raia 

 iraucre. 



The wind vane is a thin sheet of metal, (it might be of wood,) about 

 three feet long, carefully balanced by a ball of lead, and attaclied on the 

 top of a long wooden rod, which descends along the wall of the building 

 to the sill of the window of the observer. It terminates in the centre of 

 a fixed dial plate, and indicates in its movements the direction of the wind 

 by a pointer attached to the rod. 



The observer is by this arrangement enabled to determine the course 

 of the wind, by looking down on the dial plate, through the glass of the^ 

 window, without exposing himself to the starm. 



Besides the full sets of instruments furnished by the State of New York,, 

 from the apprcpriation of the Regents of the University, the Smithsonian 

 Institution has furnished a number of sets, to important stations, and in 

 order that they might be more widely disseminated, we have directed Mr. 

 Green to dispose of sets, to individuals, at a reduced price, on condition 

 that they will give us copies of the results of their Observations; the re- 

 mainder of the cost being paid by this Institution,. A number of persons 

 have availed themselves of this privilege. 



To accompany the instruments, and for the use of those who take part 

 in the Smithsonian system of meteorological observations, a series of mi- 

 nute directions, prepared by Professor Guyot, has been printed by the 

 Institution. It occupies forty octavo pages, with wood-cut representa- 

 tions of the instruments, and is accompanied by two lithographic engra- 

 vings, to illustrate the different forms of clouds, and to facilitate their 

 notations in the journals, in accordance with the nomenclature adojited bj 

 meteorologists. A set of tables has also been furnished for correcting the 

 barometrical observations, on account of variation of temperature. A 

 set of hygrometrical tables, to be used with the wet and dry bulb ther- 

 mometers, and a set, for the calculation of heights by the barometer, will 

 be prepared. 



We may also mention, in connection with this subject, that a series of 

 preliminary experiments has been made, in the laboratory of this Institu- 

 tion, for the purpose of constructing from direct observation, a scale of 

 boiling temperatures, corresponding to different degrees of rarefaction of 

 the air. With a thermometer, each degree of which occupies one inch in 

 length of the scale, the variations of the boiling point corresponding to a 

 slight change in altitude, are found to be more perceptible than those in 

 the Icnsth of the barometrical column. 



