124 we: REPORT—1849. ey PLE: 
of season in both instances, viz. the difference of tension and the form of 
curve, is very apparent from the series of summer and winter curves. 
TaBLeE XIII. 
Comparison of the excess or defect from the mean of the diurnal periods 
deduced from the observations in summer and winter. 

Season. | Mid.|2 a.m./4 a.m.|6 a.m.|8 a.m.|10 a.m.|Noon.|2 p.m.|4 p.m.}6 p.m.|8 p.m.|10 p.m.|Mean. 








—_—_— 
diy. | div. | div, | diy. | diy. diy. diy. div. | div, | div. | div. div. div. 
—~-/-/-/-—-/+]+]-]-]-]+] +4] 4 
Summer./15‘9|19°4 |18:3 | 4:0] 6:4] 9:5 378) 21 |. 2:0 1:7 |13°6 | 26:2 | 37:2 
~}/-~/-|]-]-] +/+ ]+]-|]+] 4+] + 
Winter. |77°6 | 78:9 | 79-4 |55°6 | 9-0 | 27-9 | 13:7] 3°9 | 0°6 |27°3 | 55:2 | 43-4 |102°1 





In the above table the summer and winter diurnal periods are placed in’ 
contrast. 
TaBLeE XIV. 
Synopsis of the principal points in the summer, winter, and yearly curves. 
Even. Max.| Aftern.Min. 
above below 
Forenoon. |Even. Max. 
Nocturnal | Forenoon /Afternoon | Evening 
Season. |,,... : His 3 
son. /Minimum. |Maximum.| Minimum.|Maximum. 
| | | 
div. diy, 
Summer.) 2 a.m. 10 a.m. Noon. 10 p.m. 16°7 30°0 
Winter..| 4am. 10 a.m. 4 p.m. 8 p.m. 273 55°8 
Year ...J 2am. 10 a.m. 4p.m. 10 p.m. 15:9 34°9 
The numbers in the last two columns clearly indicate a greater diurnal 
range of tension in winter than in summer; and this is very apparent from 
the curves, the upper portions of those of the winter being much bolder, and 
the depressions more distinctly marked, than the similar features of the sum- 
mer curves. It is to be-remarked, that although the diminution of tension 
between 10 p.m. and midnight is uot so great in summer as in winter, the 
precipitate downward movement of the curve, which is so strikingly apparent 
in winter, does not in the summer disappear altogether, so as to give the 
curve that gentle depression to the nocturnal minimum which characterizes 
the rise from the afternoon minimum. 
The three following tables exhibit the mean electrical tension at each ob- 
servation-hour for each month in the years 1845, 1846 and 1847, with the 
monthly, seasonal, and yearly means. The characters of the monthly move- 
ments are exhibited to the eye in the sheets of curves illustrating this report.— 
See Plates VI. VII. and VIII. 

