1" [ 1 ] 



vcrnor Brif^[^s, urging iramodiate action, and offering, on the part of the 

 Institution,"to render any assistance in our power, towards furthering so 

 huidable an enterprise. No answer has yet been received.* 



The observations made at the different military stations, under the 

 direction of the Medical Department of the United States Army, have 

 been partially re-organized, and a number of new stations, and several of 

 the old ones furnished with improved Smithsonian instruments. The head 

 of the Medical Department of tlie Armiv, Dr. Lawson, has assigned the 

 general direction of the sy.stem of observations to Dr. Mower of New York, 

 to whom we are indebted for the valuable aid which this extended set of 

 .observations wall furnish the general system. The inunediate superin- 

 tendence of the reduction of these ol)servations is in charge of Dr. 

 Wotherspoon, to whose zeal and scientific abilities, the cause of mete- 

 orology bids fair to be much indebted. 



The most important service the Smithsonian Institution has rendered to 

 meteorology during the past year, has been the general introduction into 

 the country, of a more accurate set of instruments at a reasonable price. 

 The set consists of a barometer, thermometer, hydrometer, wind-vane, 

 and snow and rain guage. 



The barometer is made by James Green, No. 422 Broadway, New York, 

 under the direction of the Institution. It has a glass cistern with an ad- 

 justable bottom, enclosed in a brass cylinder. The barometer tube is also 

 enclosed in a brass cylinder, which carries the vernier. The w^iole is sus- 

 pended freely, from a ring at the top, so as to adjust itself to the vertical 

 position. The bulb of the attached thermometer is enclosed in a -brass 

 envelope communicating with the interior of the brass tube, so as to be in 

 the same condition with the mercury, and to indicate truly its tempera- 

 ture. Each instrument made according to this pattern, is numbered and 

 accurately compared with a standard. In the comparisons made by Pro- 

 fessor Guyot, a standard Fortin barometer, by Ernst; of Paris, was em- 

 ployed; also a standard English barometer, by Newman, of London, 

 belonging to this Institution. These instruments, for greater certainty, 

 jhave been compared with the standard of the Cambridge Observatory, 

 and of Columbia College, both by Newman ; also Vv^ith the standard of 

 the 01)servatory of Toronto, Upper Canada. 



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, w^ere compared with a standard by Bunten of Paris, 

 and with another by Troughton & Simms of London. Those found to 

 .differ more than a given quantity, from the standards were rejected. 



The instruments for detecting the variation of the hygrometrical condi- 

 tion of the atmosphere, consist of two thermometers, of the same dimen- 

 sions, accurately 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 muler the 

 direction of the Institution, by Messrs. Pike & Son, 166 Broadway, New 

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



•A letter has since been receired and the sygtem placed under the direction of this Institution, 



Mis— 2 



