154 TABLES OF DIFFERENCES OF MEAN TEMPERATURES. 



We retain three periodic terms as generally siifficient for our purpose. The angle d 

 counts from midnight at the rate of 15° an hour ; at those stations where the obser- 

 vations were not made at the full hours, the angles C], Cj, Cg were changed in the 

 expression for t in order to refer them to the same epoch. The table also contains 

 the latitude (^), the longitude (X), the elevation (Ji) of the station, and the num- 

 ber of years (») of observation. The column headed T contains the annual mean 

 temperature or the mean of the twelve monthly averages. 



Numerical quantities in BesseVs fuiiction for the t> aily fluctuation of temperature, 

 on the yearly average. 



Van Rensselaer Harbor 

 Port Foulke . . . , 

 Port Kennedy 

 Boothia Felix ... 



Sitka 



Montreal .... 

 Thunder Bay Island 

 Toronto .... 

 Mohawk .... 

 Cambridge ... 

 Amherst .... 

 New Haven . 

 Brooklyn .... 

 Frankford Arsenal . 

 Philadelphia . 

 Jackson .... 

 Washington, D. C. . 

 Fort Morgan . . . 

 Key West .... 

 Rio Janeiro 



70°53' 

 73 oo 

 94 14 

 92 01 

 135 20 

 73 34 

 83 17 

 79 23 

 75 02 



71 07 



72 34 



72 57 



73 58 

 75 04 

 75 10 

 82 32 



77 03 

 88 01 

 8i 48 

 43 09 



>Y 



— 2°. 47 



+ 5-86 

 + 1-89 

 + 3-68 

 43-03 

 44-73 

 42.83 

 44.18 

 44-84 

 47-37 

 47-23 

 49.01 

 51.00 

 52.66 



51-35 

 50.90 

 53-52 

 70.24 

 76.63 

 73-75 



^, 



243° I 9' 



235 08 



254 04 

 247 24 



239 59 



221 54 



233 19 

 232 04 

 216 20 



236 07 



230 16 



231 50 



231 30 



232 54 

 224 50 



237 41 

 227 21 



222 16 



234 58 

 205 20 



o.iS 

 0.02 

 0.19 

 0.40 

 0.66 

 0.94 

 0.67 

 0.84 

 1.19 

 1.52 

 1-49 

 1-39 

 1. 01 

 1. 14 



0-93 

 2.24 

 1. 61 

 0.90 

 0.55 

 0.42 



i58°.6 



0.03 



O. II 



0.15 

 0.09 

 0.09 

 0.12 

 0.17 

 0.48 

 0.24 

 0.26 

 0.08 

 0.29 

 o. 10 



0.51 

 0-34 

 0.68 



0.21 

 0.07 



0-35 



0.22 



A better insight into the systematic character of the co-efficients and epochal 

 angles, as far as they depend upon the latitude and local conditions, can be had by 

 a combination of the results into groups. The hourly values for the stations 

 forming a group were combined into mean values, and then submitted to the 

 numerical process, which produced the following results ; — 



Types of the daily fluctuation of the temperature on the yearly average. 



Group I. The four Arctic stations. (|,^ = 74°.7 : ,„ = 82°. 5. 4 years. 



t = + 2°.23 + 2°.ll sin(0 + 24:5°.6) + 0°.14 sin(2 Q + 66°.3) 

 -I- 0.04 sin (3 9 + 216°). 



Group II. The Alaska station. ^ = 57°.l 7. 



t = + 43°.03 + 3°.46 sin(0 + 240°.0) 

 -f 0.09 sin (3 + 330°). 



Group III. Four stations in Canada and 



Northern New York. ^^, = 44°. 3 X„ = 

 t = + 44°.14 + 5°.08 sin {d + 225°.5) + 0' 

 -I- 0.21 sin (3 6 + 50°). 



= 135°.3. 13 years. 



O°.66sin(2 + 66°.6) 



77°.8. 16 years. 



89sin(2 + 48°.2) 



