156 YALE AGRICULTURAL LECTURES. 







coming thunder. In winter, the rise of mercury indicates 

 frost. In frosty weather, its fall indicates thaw, and its rise 

 indicates snow. 



4. Whatever change of weather suddenly follows a change 

 in the barometer, may be expected to last but a short time. 



5. When the barometer alters slowly, a long succession of 

 foul weather will succeed if the column falls, or of fair weather 

 if the column rises. 



6. A fluctuating and unsettled state in the mercurial column 

 indicates changeable weather. 



In these rules, the " index of the aneroid " may take the 

 place of " the mercury column." 



Prof. Silliman called to witness the experience of Mr. Jos. 

 Lesley, Jr., of Phila., one of the class who had, as a topographi 

 cal engineer, made great use of the aneroid as a levelling 

 instrument. This gentleman stated that he had used this 

 instrument during the whole season in determining contour 

 lines over hundreds of miles of broken country, and had found, 

 on calculating his lines at the end of the season, the differences 

 quite inconsiderable. He was disposed to rank the aneroid, as 

 an instrument for scientific uses, higher than Prof. Silliman had 

 placed it, but stated it was important to apply always a cor 

 rection for temperature a sort of " personal equation," varying 

 for each instrument. 



Prof. Silliman concluded by quoting still farther some of the 

 general conclusions of Prof. Henry, Prof. Coffin, Mr. Espy, 

 ^and others, as embodied in the Agricultural Reports of the 

 Patent Office and of the Smithsonian Institution. He strongly 

 advised the class to study the articles on meteorology, contain 

 ed in the documents for the years 1856 to 1860, as being far 

 the most reliable of anything hitherto within the reach of the 

 general reader. 



In the evening there was delivered a lecture by CASSIUS M. 

 CLAY, on stock and stock-breeding. 



Mr. Clay's first lecture was given in the Baptist church, 



