2^2 ON THE PERIODIC AND NON-PERIODIC VARIATIONS 
double window; its distance from the outer window being ® 
From January 1845 to the end of 1852, the thermometer shed had the additional 
protection of a second roof and a second enclosure of Venetian blinds on three of the 
sides, similar to those already described, and exterior to them at an interval of space 
from one to one and a half foot. The length of the exterior shutter on the noit ern 
side was 7 feet, and on the east and west sides 5 feet inches. The thermo- 
meter was suspended as before with the ball perfectly free, and was read from the 
inside of the observatory through a window furnished with a slidmg wooden shutter, 
which was kept closed, except at the times required for observation 
The same thermometer was employed throughout the whole period, excepting from 
March to December 1845, and in some few other occasional instances, in all of which 
corrections carefully ascertained were applied to give the values which would have 
been read by the thermometer usually employed. A comparison of this thermometer 
with a standard thermometer byFASTEE of Paris, was made at all natural temperatures 
between April 1851 and February 1852, partly with the assistance of a telescop 
and partly with the eye alone. The differences between the two thermometers at 
the several parts of the scale have been applied to all the observed temperatures 
before they were combined in the Table given in this paper. The standard thermo- 
meter by Fastee is divided <i TMle arUtraire according to the method of Regnaolt. 
The zero-points were determined as follows 
1851. Data furnished by M. Fastre . . . • 115-7 61770 
1851. By M. Izard and Capt. Lefroy at Paris 1155 617 60 
For 1° Cent. 
5-012 
5-026 
Re-examination at Toronto in 1852. 
Freezing-point. 
Boiling-point 
January 13. 
14. 
22 . 
28. 
28. 
116-12 
116-00 
116*30 
116-22* 
116-lOf 
January 5. 
12 . 
13. 
28. 
614*60 
616-55 
614-00 
614*10 
Barom. 
mm. 
743*055 
755*136 
740*866 
738-530 
617-76 
617-45 
617-57 
618*12 
212° Fahr. = 617-7- 
1 16*14=32° Fahr. 
whence 1° Cent.=5*0158; and 1 °Fahr. = 2*7865 divisions. 
This last value has been employed in the comparison in prefeience fo tie oiij 5 ina 
determination at Paris, from which however the difference is extremely slig it. 
During six years, i. e. from July 1, 1842 to June 30, 1848, the observations were 
made hourly, -Sundays, Christmas Days, and Good Fridays excepted, on which days 
no observations whatsoever were made. In the remaining six yeais, i. e. lom 
January 1, 1841 to June 30, 1842, and from July 1, 1848 to December 31, 1852, the 
• Before boiling. t After boiling. 
