Meteorological Observations at Hudson, Ohio. 319 
sixty-six hours. Assume that each rain last six hours; it is then 
,lpon an average sixty hours between two successive rains. But 
if the thermometer be 25° above the dew point, there must have 
been a considerable interval since the preceding rain; call it 
twelve —_ Rain then falls upon an average in fotty-cight 
hours more ; that is, there is an even chance that it will rain in 
iethey-for hours. If then it does not appear that extreme dry- 
ness of the air constitutes any ground to expect rain; it is at least. 
worthy of notice that it furnishes no ground for anticipating that 
it will not rain. 
‘The following are the only instances in which the dew — 
risen to 80°, all in 1838, and observed at 3 P. M. 
ee 10, 82°.1 July 28, 80°.2 
‘20, 80 .0 29, 80: .7 
a 26, 80 .0 ae pee 6,81 8 
Ser Bk aaa 
foie of t these eases a hea y ‘thunder shower followed the 
are | ; sin which the 
dew me ge rae le “zero. sar 3 bt gs be fone me in mind that 
these observations are made only at 9 A.M. and3P.M. If they 
had been made at sunrise the list would have. been larger. 
een ek BOO, 1840. 1841. 
oe. 2, 94 i. 49.0 Jan, 16, oe ae Jan.) 3; 9a. 
204 .mM.—0 4 8. 
A. mt. —3°.0 
3.P.M.— 18,9 4.m.—5 0 
; Feb, 5,3r.mM.—4.0 | 17, 3 Rls 0 19,9 a. m. —2 .0 
Nov.25,94.m.—5 0 | 25, 9 a. mu. —0 7 
wn _ WINDS. 
The chief instruction to be derived from mean observations of 
Se windei is a decision of the question, In what direction does 
the wind progress? This does not mean, towards what quar- 
ter does the wind blow most frequently. at a particular hour, or 
at.all hours, though some seem to have so regarded it. The 
Wind’s force is an element in the inquiry no less important than 
its direction, It is obvious that we cannot give a very exact and 
Satisfactory answer to this question without the aid of self- 
registering anemometers. Instruments of this kind have long 
been known, but for some reason appear not to have attracted 
much attention until recently. It is hoped that those which are 
ie AiR soon set the question at rest. Meanwhile 
»bservations, made with a vane attached to.a revolving 
shaft, wii in which the force of the wind is estimated by an 
