(hiring the Qiuirter ending March 31, 184S. 513 



the 4th, at 6'' a.m., the reading was 30-070 inches ; on the 5th, 

 at Q^ P.M., it was 29*658 inches ; on the 8th, at 9^ a.m., it was 

 30*147 inches, which was the highest value reached during 

 the month. Early in the morning of the 11th, the reading 

 passed below 29 inches, and decreased to 28*582 inches by 

 11^ a.m. on the 12th. Between this time and the 14th, at 

 midnight, the reading increased to 29*716 inches: it then 

 turned to decrease, and passed the point 29 inches on the 19th 

 at 6'ip.M., and to 28*630 inches by 6'' a.m. on the 21st; at 

 midnight, on this day, the reading was 29*330 inches, the in- 

 crease in the previous 12 hours having been as large as 0*79 

 inch; after this time the reading slowly increased to 30*000 

 inches by the 25th at 9^^ a.m. Between this time and the end 

 of the month, the lowest reading was 29*540 inches at mid- 

 night on the 27th. 



Between February 9 and March 21, the reading of the 

 barometer was below 29 inches on parts of sixteen days; nine 

 of these were in February, and seven were in March. The 

 average reading for the whole day was below 29 inches on 

 ten of these days, viz. on February 9, 10, 25, 26, 27, March 

 1, 11, 12, 20 and 21. 



I have examined the readings of the barometer on every 

 day since 1800, and 1 find the average number of instances 

 in one year that these readings have been below 29 inches on 

 parts of a day, at the height of 150 feet, is seven. In the 

 years 1829 and 1832 there was no instance of the barometer 

 reading so low as 29 inches. In the year 1809 there were 

 thirteen such instances, six of which were in December. In 

 1816 there were sixteen cases, seven of which were in January. 

 In 1817 there were seventeen cases, six of which were in 

 March. In 1820 there were seventeen cases, twelve of which 

 were in October. In 1823 there were twenty. In 1824 and 

 1825 there were fourteen in each year; in the latter year there 

 were eight in November. In 1836 there were thirteen instances, 

 nine of which occurred in February and March ; and in 

 1845 there were thirteen. Therefore there has not been any 

 similar instance in this century of such a succession of low 

 readings, as sixteen cases out of forty days. The year whose 

 corresponding period most nearly resembles that of the pre- 

 sent year in these particulars, is 1836. 



The mean reading of the barometer for February and 

 March was 29*51 inches, being less than the mean value of 

 any consecutive two months in this century, with the solitary 

 exception of the same two months in the year 1836, whose 

 mean barometer reading was somewhat below that of the |)re- 

 sent year. 



Phil. Mag. S. 3. No. 2 1 8. Siippl. Vol. 32. 2 L 



