134 REPORT—1849. 
rendered more apparent -in the summer than during the entire year. It is 
important here to remark, that the results obtained by separating the sum- 
mer observations from those of the entire year below 60 div. are of an oppo- 
site character to those obtained by dividing the aggregate observations into 
summer and winter series. In the case of the aggregate observations we 
found the summer curves representing the diurnal march, less in extent and 
less abrupt in their character than those of the entire year. On the con- 
trary, we find the summer observations of low tension rather bolder in their 
character and of greater range than those of the entire year. In the former 
case, that of the aggregate observations, the summer readings were as a mass 
much lower than those of the winter; there were also a much greater num- 
ber that would have especial reference to serene weather than of those in the 
winter, and these circumstances would reduce the summer curves to the form 
in which we find them. When however we contemplate the tensions below 
60 div., there is nothing cut off in the summer from those furnishing the re- 
sults of the year, the whole of the observations up to and including 59 div. 
finding entry at all seasons ; but we have a much greater number of low ten- 
sions during the summer than in the winter, so that a greater portion of the 
entire phenomena is as it were compressed into the lower readings, and ma- 
nifests itself by expanding the summer curves as compared with those of the 
entire year rather than contracting them. 
j 7 In tracing the diurnal march of 
| 3 3 3 : 
S = the tension below 60 div., we find 
4A.M. 104.M. 10 P.M. 24.M. 
the minimum occurring at 2 and 
4 a.M.; after 4 A.M. the tension 
gradually rises until 10 A.M., the 
epoch of the forenoon maximum ; 
a fall of 1°5 div. occurs between 
10 a.m. and noon, after which a 
very gradual and regular rise takes 
place until 10 p.m., the epoch of 
the evening maximum, which is 
succeeded by the precipitous di- 
1845, Mean. 
> ane ~~ Men. 22 minution of tension already al- 
2 luded to. In the diurnal mini- 
K 3 mum occurring at noon, and its 
ne = being followed by a gentle rise to 
2 = the evening maximum, we have re- 
peated toa certain extent the same 
47 ao : feature which we noticed as cha- 
; ‘2 yracterizing the summer curve of 
2 the aggregate observations. There 
is however one important point of 
difference which strikingly exhi- 
bits the influence of the’ higher 
tensions on the curves: the hours 
of maxima and minima are nearly 
3 summers, Mean. if not the same in both cases, and 
the gentle rise from noon to 4 P.M. 
in each instance possesses many 
features in common, the principal 
4am. 10AM. 10P.M. 2A.M. difference being a greater move- 
E ¥ ment in the aggregate than in the 
A a low tensions. The point of differ- 

Mean diurnal curves of the electrical tension below 60 div. for the summers of 1845, 1846 and 1847, with the 
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