Sun-spots and Terrestrial Phenomena. 



235 



the annual variation, combined with the annual mean value of tempe- 

 rature-range, on the scale of the period 1873 to 1880. 



6. Arranging now the results in the manner adopted by Dr. Stewart 

 in following out his hypothesis that solar activity varies with the 

 temperature-range, being inversely proportional to the mean range 

 in different months of the typical year and directly proportional to 

 the range in the same month of different years, Ave convert the several 

 monthly numbers of Table la into corresponding percentages of solar 

 activity, by multiplying them by 100 and dividing by the mean tem- 

 perature-range of all the years for the corresponding month. Table II 

 has been formed in this manner. 



The numbers in the last column vary, of course, in the same manner 

 as, though, not exactly proportionally to, the annual means of Table la. 



C. Lunar Annual Variation. 



7. The purpose of this section and the process by which it is served 

 may be described in Dr. Stewart's own words, which are as follows : — 



" It will be of interest to determine whether the temperature- range 

 has any reference to tlie relative position of the sun and moon. For 

 this purpose the whole period of observation has been portioned out 

 into lunations, beginning with new moon. Each lunation is divided 

 into eight parts, entitled— (0), (1), (2), (3), (4), (5), (6), (7) ,— (0) 

 denoting new, and (4) full moon. 



" The various lunations with the corresponding values of the tempe- 

 rature-range are exhibited in Table III. It will, however, be here 

 necessary to state how these values have been obtained. Take the 

 dates (civil time) of the four quarterly phases of the moon as given 

 by the "Nautical Almanac," and under each of these dates, as a 

 centre, group seven observations. Each value in Table III corre- 

 sponding to (0), (2), (4), (6) is thus the mean of seven separate obser- 

 vations of daily range. 



" The half- quarterly phases (1), (3), (5), (7) are then interpolated 

 in point of time, so that sometimes their date will fall upon a given 

 civil day, and sometimes between one civil day and another. In the 

 former case the mean of seven observations, and in the latter the 

 mean of six, is taken." 



The only special point that needs mention is, that only the observa- 

 tions of the 33 full years 1847 '75 to 1880 "75, including 33 complete 

 winters and 33 complete summers, are made use of in the calculations 

 of lunar variations, those of the portions of a summer or winter, 

 1847 -42 to 1847 75 and 1880 '75 to 1881 -0, being omitted. 



