358; SCIENCE OF AGRICULTURE. Part II. 



situations. These situations are combined, on account of the inequality of their revolutions, and the 

 greatest effect is produced by the union of the syzigies, or the conjunction and opposition of a planet with 

 the sun, with the apsides, or points in the orbits of planets, in which tiiey are at the greatest and least dis- 

 tance from the sun or earth. The proportions of their powers to produce variations are as follows : New 

 moon coinciding with the perigee, 33 to 1. Ditto, with the apogee, 7 to 1. Full moon coinciding with the 

 perigee, 10 to 1. Ditto, with the apogee, 8 to 1. The combination of these situations generally occasions 

 storms and tempests ; and this perturbing power will always have the greater effect, the nearer these com- 

 bined situations are to the moon's passage over the equator, particularly in the months of March and 

 September. At the new and full moons, in the months of March and September, and even at the solstices, 

 especially the winter solstice, the atmosphere assumes a certain character, by which it is distinguished for 

 three, and sometimes six months. The new moons which produce no change in the weather, are those 

 that happen at a distance from the apsides. As it is perfectly true that each situation of the moon alters 

 that state of the atmosphere which has been produced by another, it is, however, observed, that many 

 situations of the moon are favorable to good and others to bad weather. 



2337. The situations of the moon favor able to bad weather are the perigee, new and full moon, passage of 

 the equator, and the northern lunistice. Those belonging to the former are, the apogee, quadratures, 

 and the southern lunistice. Changes of the weather seldom take place on the very days of the moon's 

 situations, but either precede or follow them. It has been found by observation, that the changes 

 affected by the lunar situations in the six winter months precede, and in the six summer months follow 

 them. 



2338. The octants. Besides the lunar situations to which the above observations refer, attention must be 

 paid also to the fourth day before new and full moon, which days are called the octants. At these times 

 the weather is inclined to changes ; and it may be easily seen, that these will follow at the next lunar 

 situation. Virgil calls this fourth day a very sure prophet If on that day the horns of the moon are 

 clear and well defined, good weather may be expected ; but if they are dull, and not clearly marked on the 

 edges, it is a sign that bad weather will ensue. When the weather remains unchanged on the fourth, 

 fifth, and sixth day of the moon, we may conjecture that it will continue so till full moon, even sometimes 

 till the next new moon ; and in that case, the lunar situations have only a very weak effect. Many 

 observers of nature have also remarked, that the approach of the lunar situations is somewhat critical for 

 the sick. According to Dr. Herschel, the nearer the time of the moon's entrance, at full, change, 

 or quarters, is to midnight (that is within two hours before and after midnight), the more fair the weather 

 is in summer, but the nearer to noon the less fair. Also, the moon's entrance, at full, change, or quarters, 

 during six of the afternoon hours, viz. from four to ten, may be followed by fair weather ; but this is 

 mostly dependent on the wind. The same entrance during all the hours after midnight, except the two 

 first, IS unfavorable to fair weather ; the like, nearly, may be observed in winter. 



2339. The artificial data are the barometer, hygrometer, rain-gauge, and ther- 

 mometer. 



2340. By means of the barometer, Taylor observes, we are enabled to regain, in some 

 degree at least, that foreknowledge of the weather, which the ancients unquestionably 

 did possess ; though we know not the data on which they founded their conclusions. 

 Chaptal considers that the value of the barometer as an indicator of the approaching 

 weather, is greater than that of the lunar knowledge of the most experienced country- 

 man, and indeed of all other means put together. (Agriculture applique a Chimie, ^c. 

 We shall therefore annex such rules as have hitherto been found most useful in ascer- 

 taining the changes of the weather, by means of the barometer. 



2341. The rising of the mercury presages, in general, fair weather ; and its falling 

 foul weather, as rain, snow, high winds, and storms. 



2342. The sudden falling of the mercury foretels thunder, in very hot weather, especially if the wind 

 is south. 



2343. The rising in winter indicates frost ; and in frosty weather, if the mercury falls three or four 

 divisions, there will follow a thaw : but if it rises in a continued frost, snow may be expected. 



2344. When foul weather happens soon after the falling of the mercury it will not be of long duration j 

 nor are we to expect a continuance of fair weather, when it soon succeeds the rising of the quicksilver. 



2345. If, in foul weather, the ?nercury rises considerably, and continues rising for two or three days 

 before the foul weather is over, a continuance of fair weather may be expected to follow. 



2346. When foul weather happens soon after the falling qf the mercury, it will not be of long duration ; 

 nor are we to expect a continuance of fair weather, when it soon succeeds the rising of the quicksilver. 



2347. j(f, in foul weather, the mercury rises considerably, and continues rising for two or three days be- 

 fore the foul weather is over, a continuance of fair weather may be expected to follow. 



2348. In fair weather, when the mercury falls much and low, and continues falling for two or three days 

 before rain comes, much wet must be expected, and probably high winds. 



. 2349. The unsettled motion of the mercury indicates changeable weather. 



2350. Respecting the words engraved on the register-plate of the barometer, it may be 

 observed, that they cannot be strictly relied upon to correspond exactly with the state of 

 the weather ; though it will in general agree with them as to the mercury rising and 

 falling. The words deserve to be particularly noticed when the mercury removes from 

 * changeable' upwards ; as those on the lower part should be adverted to, when the mer- 

 cury falls from * changeable' downwards. In other cases, they are of no use : for, as its 

 rising in any part forebodes a tendency to fair, and its falling to foul weather, it 

 follows that, though it descend in the tube from settled to fair, it may nevertheless 

 be attended with a little rain, and when it rises from the words * much rain' to * rain' it 

 shows only an inclination to become fair, though the wet weather may still continue 

 in a less considerable degree than it was when the mercury began to rise. But if the 

 mercury, after having fallen to * much rain,' should ascend to ' changeable,' it foretels 

 fair weather, though of a shorter continuance than if the mercury had risen still 

 higher ; and so, on the contrary, if the mercury stood at * fair' and descends to * chan- 

 geable,' it announces foul weather, though not of so long continuance, as if it had 

 fallen lower. 



2351. Concavity of the surface of the mercury. Persons who have occasion to travel 

 much in the winter, and who are doubtful whether it will rain or not, may easily ascer- 



