216 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



" I am a farmer, and who has more opportunity and need of a "barometer 

 to study and compare than a farmer as a weather indicator ? It is now over 

 twenty-six years since I began to use one, and I have watched the changes 

 of the weather following the changes of the barometer as carefully as the 

 well educated men, and, with all due deference to their opinions, some of 

 which you have had before you, and including Comstock in his rules in his 

 Natural Philosophy for the use of Schools, I must say mj experience in 

 regard to the changes of the barometer as an indicator of the weather runs 

 counter to the rules of all of them. And yet, I do believe that barometers, 

 with correct general rules — rules founded on correct principles — may be 

 and are of great use to farmers. 



"Comstock, in his rules for schools, says: 



" ' Rule 1. In calm weather, when the wind, clouds or sun indicates 

 approaching rain, the barometer is low.' 



" Reply. The average height of the barometer is about 30 inches. Two 

 years ago, the fore part of this month, the barometer stood at 343.30 inches 

 for several days, with a gentle wind from the southeast, air warm and very 

 humid, with light showers. The wind shifted early on seventh day morn- 

 ing to the northeast, the barometer began and continued to fall through the ' 

 day, and we had, from nine o'clock until night, one of the greatest rain 

 storms ever known here. I have known snow storms, barometer 30.50, and 

 it was quite rainy IVth inst., barometer 30.12 inches. 



" ' Rule 4. During the coldest, clear days, when a gentle wind from the 

 iiorth or west prevails, the mercury stands the highest.' 



" Reply. On the 16th inst., the barometer rose the highest it has been for 

 more than eight years — wind northeast, and not freezing cold. It clouded 

 over and threatened rain while the barometer was reaching that height. 



" ' Rule 5. After great storms, when the mercury has been lowest, it rises 

 most rapidly.' 



" Reply. I have known it to stand at 29.50 for a whole day after a storm, 

 wind hard from northwest. 



" ' Rule 8. When it rains, with the mercury high, we may be sure it will 

 soon be fair.' 



" Reply. My reply to the first rule will apply with equal force to this, 

 and beside that, it clouded over and threatened rain: 16th inst., barometer 

 30.82, rain; 17th, 30.72, rainy; 18th, 30.30, rainy; 19th, 29.75, rainy; 20th, 

 barometer 29.75 — making five rainy days after a very high state of the 

 barometer, and four after it began to rain, I have observed many times 

 that the fall of the barometer alone does not indicate rain; neither does a 

 rise always denote fair weather — but often exactly the reverse. 



"The laws which govern the changes in the weight of the atmosphere 

 are similar in some respects to those which govern the tides. Much is 

 caused by reaction. When we see a low tide we know to a reasonable 

 certainty that the tide must rise to fill the apparent vacuum between that 

 and a medium tide. So with the barometer: when it falls low, or very low, 

 we know to a reasonable certainty that a northwest wind must follow soon, 

 because the rise in the barometer is generally caused by a northwest wind. 

 The velocity of the wind, after the change, is generally in proportion to the 

 lowness of the barometer and its time of duration from that quarter is 



