120 REPORT—1849. 
TABLE VI. 
Number of positive readings at each observation-hour in the three summers 
of 1845, 1846 and 1847, 

Year.| 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./Sums, 


1845.) 135 | 135 | 147 | 176 | 174 | 167 | 135 | 146 | 149 | 152 | 158 | 171 | 1845 
1846.| 140 | 149 | 155 | 172 | 175 | 170 | 142 | 135 | 139 | 138 | 148 | 169 | 1832 
1847,| 125 | 148 | 163 | 177 | 178 | 173 | 139 | 137 | 141 | 140 | 147 | 169 |1837 






Sums.) 400 | 432 | 465 | 525 | 527 | 510 | 416 | 418 | 429 | 430 | 453.| 509 | 5514 
These numbers are more nearly equal in their amount than the yearly 
distribution, 
Tas_eE VII. 
Mean electrical tension at each observation-hour in the three summers of 
1845, 1846 and 1847, with the mean diurnal period of summer. 
Year.| 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. 
— —| —___. 


—| —— 









div. | div. div. | div. | div. diy. div. | div. | div. | div. | div. div. div. 
1845.| 19-6} 16°0| 17°3| 29°1| 39°4| 34:8 | 29°6| 33°8| 32°6| 36°6| 53°6] 711 | 35°3 
1846.) 21°0) 17:4} 19°4| 33°9| 44°9| 47-1 | 34°9| 33°9| 36:3] 40-4] 49-1} 55°0 | 36°5 
1847.) 23°5| 20°0| 19°8 | 36°7 | 46°5| 57-9 | 35°4| 37°8| 37°0| 39°8| 49°7| 64:2 | 39°7 
—~-| — E ————_ | | —— — ] —-———_ 



Mean.| 21°3) 17:8 | 18°9 | 33°2| 43°6| 46°7 | 33°4| 35°1| 35:2] 38°9/ 50°8) 63:4 | 37-2 



TaBLe_e VIII. 
Excess or defect of the mean electrical tension at each observation-hour as 
compared with the mean of each summer in the years 1845, 1846 and 
1847, and the mean of the three summers. 

Year.| Mid.|2 a.m./4 a.m.|6 a.m.|8 a.m.|10 a.m.|Noon.|2 p.m.|4 pm.|6 p-m.|8 p.m.|10 p.m./Mean. 



div. | div. diy. div. | div. div. div. div. div. | div. div. div. div. 


— | - + + | + | + 
1845.| 15-7) 19°3| 18:0} 6:2 | 4:1 | O05 | 5:7 | 15 | 2:7 | 1:3 |18-3 | 35°8 | 35°3 
—|—- + | + + | + | + 
1846.} 15-5) 19°1| 17°1| 2°6 | 8:4 | 10°6 16 | 2°6 | 0:2 | 3:9 |12°6 | 18:5 | 36°5 
— | - + | + + | +) + 
1847.| 162) 19°7| 19°9| 3:0 | 68 | 18-2 4:3 | 199 | 2:7 | O01 |10°0 | 24:5 | 39-7 





—|/=}/—-)-}+}4)-}-]};-]+ |4) 4 
Mean.| 15°9; 19-4} 183} 4:0 } 6:4 9°5 38 | 2°71 | 2°0 | 1-7.)13°6 | 26:2 | 37:2 


In contrasting the numbers in Tables VII. and VIII. with those in Tables 
IV. and V. having reference to the entire year, we are struck with the greater 
uniformity that prevails among those appertaining to the summer. The 
means approximate more closely to each other, the general course of the 
numbers is more regular, and the rise during the morning hours more gentle, 
although there is still a considerable diminution of tension between 10 p.m. 
aud midnight. 
In contemplating the numbers in Table VIII., indicating the excess or de- 
fect in comparison with the mean, we sce atta glance that the double pro- 
gression is well exhibited: at noon, 2 and 4 p.m., the numbers are in defect, or 
lower than the mean, as well as at midnight, 2,4 and 6 a.m. It may be 
proper to mention here, that during the summer months the tension seldom 

