METEOROLOGICAL REGISTER KEPT AT LE1TH FORT IN 1826 AND 1827. 361 



mean of two ordinates, we may deduce the mean temperature of the whole year ; 

 that is, the mean of all the horary ordinates." 



As meteorological registers have sometimes been kept only once a day, it is 

 desirable to ascertain the relation of the mean temperature of each hour to that 

 of the day. In the following Table, I have given the results for 1826 and 1827, 

 and also for 4 years, from 1824 to 1827 inclusive : — 



Hour. 

 1 A.M. 



1826. 

 -2-552 



1827. 

 -L706 .. 



Mean of Four Tears 

 1824-1827. 



—2-131 



2 



-2-903 



—2015 .. 



— 2396 



3 



-3-179 



-2-298 .. 



—2-658 



4 . . 



-3-228 



-2-308 .. 



— 2-793 



5 . . 



-3314 



-2-316 .. 



—2844 



6 



-2-943 



-2-011 



—2-545 



7 



-2-335 



-1-524 .. 



—1-956 



8 



-1-393 



-0-853 .. 



—1-180 



9 



-0-121 



-0-096 .. 



— 0-760 



10 



. +0-970 



+0-647 .. 



+0-777 



11 



. +1939 



+1-504 .. 



+ 1-702 



12 



+ 2-746 



+2-088 .. 



+2-463 



1 P.M. 



. +3-256 



+2-440 .. 



+2-865 



2 



+ 3-490 



+2-614 



+ 3-125 



3 



+ 3-473 



+2-536 .. 



+3-135 



4 



+ 3-411 



+2-353 .. 



+2-927 



5 



+ 3065 



+ 2028 .. 



+2-576 



6 



+•2-447 



+1-433 



+1-984 



7 



+ 1-442 



+0-845 .. 



+1-211 



8 



+ 0-383 



+0-350 .. 



+0-362 



9 



-0-460 

 -0-964 



-0-304 .. 



-0-852 .. 



-0-410 



10 



—0-949 



11 



-1-432 



-1-044 



-1-351 



12 



-1-798 



-1-318 .. 



-1-713- 



From this Table it appears, that the mean annual temperature of any hour never 

 differs more than 3i° from the mean temperature of the day for the whole year. 

 The very same result was obtained from the Register of 1824 and 1825.* 



V. — On the Parabolic form of the Four Branches of the Annual Daily Curve. 



In the report upon the Register for 1824 and 1825, 1 have shown that the four 

 branches of the annual daily curve approach so nearly to Parabolas, that the 

 greatest difference between the observed and calculated temperatures is only a 

 quarter of a degree of Fahrenheit. The following Table contains the calculated 

 temperatures for 1826 and 1827, and the difference between them and the observed 

 temperatures : — 



Edinburgh Transactions, vol. x. p. 387, 388. 



