METEOROLOGICAL OBSERVATIONS AT PLYMOUTH. 



31 



the mean points were first marked off, and then a continuous line was passed 

 through them by means of a flexible batten, so as to include the greatest 

 number ; the points of deviation from such a continuous and fair curve being 

 marked by a star. Now, I have to call the attention of the Association to 

 the surprising coincidence in the general character of all these lines, and the 

 very few and small deviations which they present ; a result which I cannot 

 but deem somewhat remarkable, considering the frequent atmospheric dis- 

 turbances to which we are liable in these latitudes. The observations them- 

 selves must have been most carefully made, otherwise such a constant result 

 could not possibly have been arrived at ; and I cannot but deem it my duty 

 to impress on the Association, the propriety of preserving with great care the 

 original manuscript of the observers and printing the whole series, as being 

 calculated to advance the present state of meteorology. The meteorologist 

 will have then at his command a series of hourly records obtained at con- 

 siderable cost in money and time, of as unexceptionable a character as in 

 the nature of the circumstances under which they have been made, and the 

 present state of science, it is possible to obtain. 



Table, containing the mean hourly pressures for each of the years 1837> 1838, 

 1839, 1840 and 1S41, together with the mean of these years from 43,800 

 observations, at 75 feet above the mean level of the sea, reduced to 32° of 

 Fahrenheit's scale. — The periods of maxima are denoted by the sign +, 

 the minima by the sign — , and the mean by a *. See pi. iv. 



I have little further to observe on this table ; the differences from the ge- 

 neral results already deduced in my Report for 1839 not being considerable, 

 the mean pressure of the five years corresponding with that already obtained. 

 I may briefly remark that from the series of five years we find the line of 

 mean pressure crossed between the hours 1 and 2, and 7 and 8 a.m., and 

 again between 12 and 1, and 6 and 7 f.m. The hours of max. pressure are 



