220 BOARD OF AGRICULTURE. 



metallic box, the cover of which is very thin, and Corrugated, or in 

 ridges and furrows, concentric with the walls. The air is exhausted 

 from this box, which is then hermetically sealed. The rusult is, 

 that the elastic cover rises and falls with every change in atmos- 

 pheric pressure. By means of a combination of levers and springs, 

 these movements are communicated from the center of the cover to 

 a pointer which moves over the graduated face of the dial, on which 

 inches and hundredths are inscribed, which correspond with the 

 hight of the column in the mercurial instrument. The whole appa- 

 ratus is incased in a brass box, about four inches in diameter and 

 two inches deep, covered with a front glass, and resembling in gen- 

 eral appearance a chronometer case." 



Having tested Mr. Kendall's barometer to my own entire satis- 

 faction, and knowing others who have also done so, and being re- 

 peatedly assured that they have often saved their cost in a single 

 haying season, I give it a hearty commendation, and take this meth- 

 od to introduce it more generally to the notice of Maine farmers. 

 None should, however, expect that as a weather prophet the barom- 

 eter will be found of unerring accuracy and exactness, for no 

 infallible means of j^redicting approaching changes have yet been 

 discovered. The state of the weather depends upon various con- 

 ditions, of which the weight or density of the atmosphere is but 

 one — the amount of moisture contained in it, is another ; tempera- 

 ture is a third, electrical changes a fourth, and so on. Then again, 

 local causes have much to do with the weather in any given local- 

 ity. But in connection with the ordinary appearances in nature, 

 which all persons more or less observe, and which from time imme- 

 morial have been recognized as indicating changes, the barometer 

 renders exceedingly valuable assistance in judging, and the more 

 so that its testimony touches a point which we have no other 

 means of ascertaining ; (i. e., the density of the atmosphere at the 

 time.) 



As before remarked, the average hight of the barometer at the 

 sea level, is about thirty inches. As we ascend from this level the 

 mercury falls, for the simple reason that we leave a portion of the 

 atmosphere beneath us, and of course there is less weight above. 

 Every hundred feet we rise, the column falls about a tenth of an 

 inch, so that it is no particular hight which indicates cither fair or 

 foul weather, but we judge only by the changes. 



rrof. Silliman gives the following rules which embody the re- 

 sults of long and various experience in dillcrcnt places. 



