Emerson.] ^^" Oct. 21, 



■with Jt set of instruments, consisting of a barometer, two thermometers 

 (one self-i'egistering), and a rain-guage.* The manufacture and distribu- 

 tion of these instruments was all entrusted by the Committee to my own 

 Supei'vision. Most, if not all, of these instruments doubtless exist at the 

 present day, in the court-houses or academies in the counties to which 

 they Avere sent. 



At the time to which I refer, I was much devoted to meteorological 

 investigations, and for several years delivered lectures on meteorology, 

 before the class of the Franklin Institute. I made observations several 

 times a day, noting the atmospheric changes as to density, temperature, 

 dew-point, winds, aqueous precipitations, &c. «&c. It was whilst so 

 engaged, that I made a communication to this Society, relative to the 

 inapplicability, in this country, of the prognostic words inscribed on the 

 scale-plates of European barometers, such as fair, set fair, rainy, &c., 

 which generally indicate the reverse of the prognostic on this side of the 

 Atlantic, where the barometer has never acquired any high degree of 

 credit as a weather-glass. "Stormy" is, perhaps, the only inscription 

 which might be retained for both sides of the Atlantic at or near the sea- 

 level. 



In the course of my observations, I found that storms from the north 

 and north-east were generally preceded by high risings in the barometer, 

 especially during the winter months. This observation was recognized 

 as original by Sears C. Walker, a distinguished member of this Society, 

 and by Mr. Espy, who regarded it as one of the main supports of his 

 theory of storms. My communication upon these subjects, I suppose, 

 still exists among the manuscripts in the archives of this Society. In 

 reference to the barometers made for distribution in this State, it is 

 worthy of notice that they do not contain the European inscriptions on 

 their scale i)lates, "fair," "set fair," &c., which, as I have already 

 stated, are calculated to mislead observers on the western side of the 

 Atlantic, and bring the instrument into discredit. Another reason for 

 omitting the inscriptions exists in the fact, that many of the barometers 

 went to points in the State so greatly elevated as to render deceptive and 

 useless any inscriptions made on scales graduated from the sea level- 

 The main consideration of the Committee was to ascei'tain the fluctua- 

 tions of the mercurial column as influenced by atmospheric conditions. 



In pursuing his investigations concerning the phenomena connected 

 with the origin and movements of storms, tornados, and water-spouts, 

 Mr. Espy was chiefly indebted for his data to the materials brought to- 

 gether by the labors of the "Joint Committee," from which he was 

 enabled to map the courses of many remarkable storms, hurricanes and 

 water-spouts, which drew marked attention from men of science at home 

 and abroad. 

 In 1840, Mr. Espy went to Europe, and laid his views before the British 



*The original standard barometer and thermometer from which the other instruments were 

 graduated, are now in tlie possession of tlie Franli 



