SECRETARY'S REPORT. 219 



is of great value to the sailor upon the ocean, and few or no ships 

 Bail without being provided with one. It is also of exceeding value 

 to the farmer, especially in haying and harvesting time. But there 

 are serious objections to the mercurial barometer for farmers' use, 

 which have prevented its general introduction. One of these is its 

 cost, growing out of the great care necessary in its manufacture, to 

 render it perfect, in depriving the column of every particle of air, 

 which is done by boiling the mercury in the tube, and by other 

 means involving considerable labor and expense. Inferior instru- 

 ments are sold as low as seven to ten dollars, but reliable standard 

 instruments sell for a much higher price. Other objections are its 

 liability to break and to get out of order. 



Recently, another form of the instrument has been invented, which 

 in many respects is much preferable, and is known as the Aneroid 

 Barometer. • The name is significant of the formation of a vacuum 

 without a fluid, and the form of this barometer is greatly in contrast 

 with the Torricellian tube. The principle on which this instrument 

 operates seems to have been first noticed by M. Conte, a French 

 professor, but was finally reduced by M. Vidi. At the New Haven 

 agricultural lectures, in February last, Prof. Silliman, Jr., devoted 

 an hour or two to the subject of Meteorology, in which he described 

 the various forms of this instrument. Of the Aneroid barometer, 

 which he deemed the most important instrument that could be 

 placed in the hands of the farmer, he said : " Unqualifiedly it is the 

 best for the farmer's use ; and for the scientific man, its portability, 

 and almost total unliability to accident, strongly recommend it. The 

 old mercurial barometer, with its marks of ' cloudy,' ' rain,' ' fair 

 weather,' &c., is utterly unreliable ; for the pressure of the atmos- 

 phere at divers bights is different, and the pressure that near New 

 York rises to ' fair weather,' would at a higher place, say the prai- 

 ries, stand at 'foul.' And then, again, if roughly handled, air will 

 leak into the instrument, and its value be utterly destroyed. The 

 * Aneroid' baronieter (or the 'without fluid' barometer) was first 

 invented by M. Conte, a professor at the jErostatical School at 

 Meudon, near Paris, but a Yankee mechanic, Mr. Edwin Kendall, 

 at New Lebanon Springs, N. Y., has made it much cheaper, and 

 equally reliable as the expensive French instrument." He sells it 

 for the moderate Drice of ten dollars,* only one-third the cost of a 

 Smithsonian barometer. The Aneroid consists of aflat and circular 



♦While the above is in press, (Dec. 8th) I am advised by Mr. Kendall that he has 

 reduced the price to $7.50. 



