144 REPORT—1849, 
epochs of the forenvon and evening maxima. It is however much more 
equable, the difference between the greatest and least numbers, excluding the 
11 at 6 a.M., being only 106. A proportionate regularity in the diurnal march 
may consequently be expected. 
TABLE XLII. 
Mean electrical tension above 60 div. at each observation-hour in the three 
winters of 1845, 1846 and 1847, with the mean diurnal period of winter. 
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. 
a | a |e | | ee | ef | 
div. | div. div. div. div. | div. div. | div. div. div. 
BAG: Wacuicel ccs voe | see cee 85:0 |184°8 | 231°1 |188-0 |146°6 |139-6 [167-0 |223°1 | 259-1 {196-0 
RAG ss tod ..se bas] Ses Sie 83:3 }130°4 | 163-2 |171-9 |145-0 |136°9 {174-5 |198-7 | 164-7 |161°1 
sa ae ee Poe 165-0 |206:0 | 248-0 /261°1 |257-1 |235-0 |244°8 |247-4 | 221°8 |238-7 
MlGame| ire. -2} sodsas'| saves. 105°9 |172:9 | 213°3 |206°3 |180-9 |169-0 |194°6 |223°3 | 213°6 |197°9 
— 
Tasie XLIII. 
Excess or defect of the mean electrical tension above 60 div. at each ob- 
servation-hour, as compared with the mean of each winter in the years 1845, 
1846 and 184-7, and the mean of the three winters. 
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. 

-}-|/+]/-/-|;-/-/4] 4 
MB AD eases tasedcs [iwacens 111°0} 11°2| 35:1 8:0| 49°4| 56:4] 29:0) 27-1] 63°1 |196°0 
—~|-|+}4+}—/-J/+]4] 4 
TSG ics salted enn Newet a6 77°8| 30:7} 2:1 | 10°8} 161) 24:2] 13-4) 37°6| 3°6 |161°1 
—-—|-|/ + —~|+]+] - 
OSE ie becoce lr Rececll |eacas 73°7 | 32°77) 9:3 | 22:4] 184] 3:7) G61] 8:7] 169 |238-7 
~|—-|+/+/—-|-|/-]+] + 
IMPGAI. | iwac| \etaanell caseee 92°0| 25°0; 15°4 8:4| 17:0! 28-9] 3:3] 25:4] 15°7 |197-9 
There can be no question that a much greater regularity of movement 
characterizes these periods than we found appertaining to those of the entire 
year. In each of them we find the two maxima well-developed ; in the win- 
ter of 1847 the forenoon maximum was the highest, but in other respects they . 
agree more or less closely with the aggregate winter curves. The diurnal 
march is well-traced: commencing at 8 A.M., we find the forenoon maximum 
attained at 10 A.m., then a well-marked fall until 4 p.m., the afternoon mini- 
mum, after which a regular and rather rapid rise until 8 p.m., the epoch of 
the evening maximum, which is followed by a diminution of tension at 10 p.m. 
The annexed curves (fig. 10), which may be well compared with those on 
page 143, exhibit all the winter phenomena of high tension with considerable 
distinctness. It may be remarked, that in 1845 the evening maximum oc- — 
curred at 10 p.m., and that a close agreement, in this respect, obtains be- 
tween the high tension and aggregate curves in the winter of 1845. 
In our remarks on the winter curves of aggregate tension (see page 123), we 
noticed the influence which the winter curves exerted on those of the entire 
year, and suggested the probability that the higher tensions materially in-_ 
fluence the general results. This is very strikingly illustrated by the com- — 
parison of the winter curves of high tension with those of the same season as — 
deduced from the aggregate observations; the main features of the curves in 
both series are similar, the principal difference consisting in the values of the 

