METEOROLOGICAL OBSERVATIONS AT PLYMOUTH. 



163 



Daniell's result, '015, and take the morning negative oscilla- 

 tion for Edinburgh = '0106 as a near approximation to the 

 mean, then we have the following series : — 



Table XVII. 



Latitude, 



50.21 



50.51 



53.56 



55.55 



Oscillation 



•0168 



•0150 



•0134 



•0106 



By which we perceive that the amount of the oscillation is less 

 in the greater latitudes. 



Professor Forbes's formula "11 93 cos^ 5 — '0150, &c., cannot 

 exactly correspond with these numbers, except the last, since 

 his index of the cos . $ w^as obtained by selecting observed 

 oscillations between 10 and 4 a.m. According to this formula 

 we should have for the oscillations at these latitudes, 



Plymouth. London. York. Edinburgh. 



'0238; -0^27; '0167; -0130. 



Now the formula gives a fair approximation to the evening 

 oscillations at these places, which are — 



Plymouth. London. York. Edinburgh. 



•0204; -0230; '0170; '0097. 



It may be further remarked as a curious coincidence, that 

 the night oscillation at London corresponds with the morning 

 oscillation at Plymouth, whilst the morning oscillation at York 

 corresponds nearly with the night oscillation at Plymouth. 



Average Monthly Pressure, 



In Table IV. we have given the average monthly pressure 

 for the years 1837, 1838, 1839, together with the mean of these 

 years, by which it will be perceived that the annual variations 

 have not for this period of time been at all regular. 



Thus in the year 1837 the maximum occurred in October, 

 and the minimum in September, the mean about July, whilst in 

 1838 the maximum occurred in July, the minimum in Novem- 

 ber, and the mean in January ; in 1839 the maximum occurred 

 in April, the minimum in September, and the mean about 

 June. 



The table, however, upon the whole, indicates a maximum 

 and minimum towards the close of the year, and a mean in 

 spring, which perhaps will become more apparent by an in- 

 creased number of observations. 



In the following table will be found the deviations from the 

 mean of the three years through the different months, in which 



M 2 



