OBSERVATIONS OF THE EDINBURGH ROCK THERMOMETERS. 



177 



accuracy attainable is sufficient for the purpose ; (2) because the fifty-two weekly mean 

 temperatures could be divided up into twelve lots, eight of four each, and four of five 

 each, the means of which would not differ much in weight, and these monthly means 

 could be used in solving the equations, without having to resort to the necessity of 

 interpolating values from the curves themselves, a method which is not so accurate, 

 unless the curves are drawn on a very large scale. The year was then divided into 

 twelve equal parts, starting from the mean date of the first Mod day. This date for the 



365'25 



forty years is January 4"10. If to this we add __ = 30*4375 days, and consider 



February as consisting of 28 "25 days, we arrive at the following twelve equi-mensual 



dates. 



4-10 July, . . . 5-48 



February, . 



. 3-54 



March, 



. 5-72 



April, 



. 5-16 



May, 



. 5-60 



June, 



. 5-04 



August, 



. 4-93 



September, 



. 4-35 



October, 



. 4-79 



November, 



. 4-22 



December, 



. 4-66 



As, however, the mean dates of the four or five weekly mean temperatures used in 

 forming the twelve monthly means did not generally come out quite the same as the 

 equi-mensual dates, it was necessary to apply a small correction depending on the rate 

 of increase or decrease of temperature at the time. This correction is always small, its 

 greatest values being +0 C, 015 in the case of t x and -f-0°"208 for t 4 . The following table 

 gives the monthly mean temperatures thus deduced, and their dates for the old 

 thermometers from forty years' observations, except in the case of t 2 , of which only 

 twenty-four years' observations had been secured at the date of its fracture. 



OLD THERMOMETERS. 



Equi-mensual Date. 



'i 



h 



h 



h 







°F. 



°F. 



°F. 



°F. 



January, 



4-10 



47-876 



47-358 



44-324 



41-346 



February, 



3-54 



47-789 



46-297 



42-876 



40-150 



March, 



5-72 



47-572 



45-386 



42-169 



40-003 



April, . 



5J6 



47-275 



44-811 



42-382 



41-407 



May, . 



5-60 



46-975 



44-737 



43-868 



44-535 



June, . 



5-04 



46-736 



45-275 



46-214 



48-462 



July, . 



5-48 



46-629 



46-376 



49-007 



52-164 



August, 



4-93 



46-690 



47-672 



51-073 



53-945 



September, . 



4-35 



46-922 



48-756 



51-701 



53-416 



October, 



4-79 



47-256 



49-292 



50-858 



50-829 



November, . 



4-22 



47-582 



49-163 



48-800 



46-789 



December, . 



4-66 



47-813 



48-412 



46-168 



43-330 



T„ = 



47-2596 



46-9612 



46-6200 



46-3647 



