METEOROLOGICAL OBSERVATIONS AT PLYMOUTH. 



33 



sion of the scale. I have in this way endeavoured to arrive at something like 

 an approximation to the velocity and direction of what I believe would 

 amount to a trade-wind in the place of observation. The general type of the 

 wind, as laid off on the principles suggested by Mr. Whewell, I have now 

 the pleasure of exhibiting to the Section ; and it will be seen that it furnishes 

 a general resultant, directed from about S.S.W. to N.N.E., being from the 

 southerly to the northerly points of the compass*. 



In the annexed table will be found the mean velocity of the current for 

 each successive month, taken without regard to direction, together with the 

 mean velocity for the whole year ; the period of observation being from April 

 1841 to April 1842. 



Table showing the mean velocity of the wind by Whewell's Anemometer. 



As I do not pretend to a degree of precision in these first results greater 

 than is requisite to entitle them to consideration as useful and important ap- 

 proximations to a more refined inquiry, I have not thought it requisite to 

 treat them more elaborately than their present state demands. If we dimi- 

 nish the mean velocity arrived at in this table, in the proportion of the whole 

 length or trace of the wind described, to the general resultant, we shall have 

 some general idea of the course and velocity of the aerial current, as deduced 

 by this species of inquiry. Now the whole space described in this case is to 

 the resultant as 2 : 1 nearly ; we may therefore take the resulting velocity at 

 about 4*5 miles an hour, and the general direction as N.N.E. 



I shall be prepared to lay before the Section at our next meeting, typical 

 delineations of the wind for 3 years, as deduced by this instrument, accom- 

 panied by more extended and corrected results than have been as yet arrived 

 at. I hope what has been done is sufficient to show, that the instrument it- 

 self is capable, when well employed, of furnishing highly important results. 

 It would necessarily have failed under the form in which it was first placed 

 in my hands ; but set up as stated in my Report for 1840, and constructed 

 in a firm and solid way with little friction, I believe it highly calculated for 

 meteorological observation. But whether we register by this or any other 

 instrument the daily direction of the aerial currents, I feel persuaded that 

 little advantage will ever be derived to meteorology, unless the observa- 

 tions be reduced to the form prescribed by Mr. Whewell, who has certainly 

 taken the only correct view of the nature of such observations. Without 

 deducing the integral effect of the wind, that is to say, a space proportional 

 to that which a particle of air would pass over in a given time, taking into 

 account the velocity of the wind and the time for which it blows, we can 



* The mean velocity has been deduced by determining a value of V 2 for every 24 hours, a 

 method which, although not mathematically exact, is still sufficiently approximative for our 

 present purpose. 



1842. D 



