ON PROPOSED AMERICAN METEOROLOGICAL OBSERVATIONS. 323 



made by Ernst of Paris, was used, and also a standard English barometer by 

 Newman of London, belonging to this Institution. These instruments, for 

 greater certainty, have been compared with the standard of Cambridge 

 Observatory, and of Columbia College, both by Newman, and with the 

 standard of the observatory of Toronto, Canada West. The results of these 

 examinations prove the barometers made by Mr. Green, according to the 

 plan adopted by the Smithsonian Institution, to be trustworthy instruments. 

 The thermometers are by the same maker, and those intended for the State 

 of New York were compared with a standard by Bunten of Paris, and 

 another by Troughton and Simms of London. Those found to differ more 

 than a given quantity from the standard were rejected. 



" The instruments for detecting the variation of the hygrometrical condition 

 of the atmosphere consists of two thermometers of the same dimensions ac- 

 curately graduated. The bulb of one of these is enveloped in a covering of 

 muslin and moistened with water, and that of the other is naked. 



" The rain and snow-gauges, and also the wind-vanes, are made under the 

 direction of this Institution by Messrs. Benj. Pike and Son, 166 Broadway, 

 New York. The rain-gauge is an inverted cone of sheet zinc, of which the 

 area of the base is exactly 100 square inches. This cone or funnel ter- 

 minates in a tube which carries the water into a receiving vessel until the 

 end of the rain. The water which has fallen is measured by pouring it into 

 a cylinder so graduated as to indicate hundredths of inches of rain. A 

 smaller cylinder is also provided which gives the thousandths of inches of 

 rain, and may serve in case 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 it mouth down- 

 ward to the bottom of the snow where it has fallen on a level surface, and 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 glass graduated cylinders of the rain-gauge. 



" 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 supported 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 at- 

 tached 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 storm. 



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

 from the appropriation of the Regents of the University, the Smithsonian In- 

 stitution has furnished a number of sets to important stations ; and in order 

 that the instruments may be more widely disseminated, have directed Mr. 

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

 they will give copies of the results of their observations ; the remainder of 

 their 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 minute 

 directions, prepared by Professor Guyot, has been printed by us, occupying 

 forty octavo pages, with woodcut representations of the instruments. This 

 is accompanied by two lithographic engravings to illustrate the different 



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