24 Lovering and Bond on Magnetic Observations at Cambridge. 
St. Petersburg, 1837. 
/ / 
April 16.2 October 6.7 
May 15.1 November 3:7 
June 16.5 December 1.9 
July 13.6 January 3.2 
August 11.9 February 5.8 
September 9.9 March 11.0 
83.2 32.3 
13,86 5.4 
We have no occasion in this place to remark on the cause of this 
great inequality of arc in the different months, or on the times when 
the maximum and minimum occur. We only wish it to be observed 
that the daily curve, so perceptible in other places ‘and so marked 
by its general uniformity of appearance, is clearly seen in the Cam- 
bridge observations. We have here referred to the Plates which 
represent some of these diurnal curves, but Table II. at the end 
will display in a condensed form, the results of 12 months’ obser- 
vation on this point. As the values for some of the months were 
deduced from scanty observations they cannot be brought into a 
fair comparison with more comprehensive means. If it shall appear 
that the times of maximum and minimum declination are embraced 
within the limits of a few hours, it is extremely important that ob- 
servations should be made during those periods every day in the 
year to determine the precise moment when they occur each day 
and the arc of excursion. Means drawn from such abundant data 
might lead to a satisfactory solution of the daily changes and not 
leave them, as at present, to probable conjecture. 
It appears from observations on various parts of our planet that 
periodical changes of days, months, years, and longer duration are 
