MAGNETIC DECLINATION AT TORONTO, ST. HELENA, AND HOBARTON. 551 
tingen V7as then applied, so as to give the mean Gottingen time of the moon’s passage 
of the astronomical meridian of Toronto. The observation at the Gottingen hour 
nearest to the time thus computed was then marked with signifying that it was 
the nearest observation to the moon’s upper culmination, and from which its distance 
could not exceed half an hour. The time of the moon’s inferior passage was then 
computed in a similar manner, and the observation at the Gottingen hour nearest to 
it was marked 12Ji. The intermediate hours received corresponding markings, except 
that on those occasions when thirteen solar hours, and consequently thirteen obser- 
vations, were comprised within twelve lunar hours, that observation was omitted which 
fell most nearly equidistant between the epochs of two exact lunar hours. The obser- 
vations were then considered to be prepared for arrangement in lunar tables, but 
instead of the observations themselves, the differences at each hour between the scale- 
reading observed and the mean scale-reading in the same month and at the same 
hour were entered in these tables, by which process the diurnal and other variations 
depending on the time of the solar year and the hour of the solar day were, in great 
part at least, eliminated. The differences were marked with a -j- or — sign accord- 
ing as the scale-reading at the time of observation was greater or less than the 
monthly mean at the same hour ; the entries having a -f- sign implying a more 
westerly direction of the north end of the magnet than its mean direction in the 
same month and at the same hour ; and those having a — sign implying the con- 
verse. The mean was then taken, in every month, of every lunar hour (taking the 
signs into account); the monthly means were collected into yearly means, and 
finally, the means at each lunar hour in each of the six years of observation were 
collected in a single table. 
The whole number of observations in the six years at Toronto which were thus 
treated amounted to 44,754, of which 6356 were put aside in consequence of the 
amount of disturbance (measured from the monthly mean at the same hour) equal- 
ling or exceeding 2''9 in arc. 
The following Table shows the amount of Easterly or Westerly deflection of the 
north end of the magnet at the different lunar hours derived from the observations of 
the six years by the process which has been described, and inferred to be due to the 
moon’s action. The partial results, or those afforded by the separate years, will be 
printed in the introduction to the third volume of the Toronto Observations. They 
exhibit only such small partial differences from the mean of the six years as may 
reasonably be ascribed to the operation of other causes than the moon’s influence; 
and present no notable trace of a progressive increase in the amount of the variation in 
the successive years from 1843 to 1847, such as that which has been found to charac- 
terize the variations depending upon the solar hours. 
The deflections in the subjoined Table are in scale divisions, of which each =0''721. 
The readings to which the — signs are prefixed denote Easterly deflections, and those 
which have the + signs prefixed Westerly deflections. 
MDCCCLIII. 4 c 
