* 
ON MAGNETICAL AND METEOROLOGICAL OBSERVATIONS. 23 
of different other places, I have lately remarked a circumstance that seems 
to me in the present discussion not unworthy of attention, viz. that the form 
of the daily curves, as given by the monthly means, is nearly the same every 
year, while the magnitude of the curves or the meam daily range differs con- 
siderably from one year to another; thus, for instance, the curve representing 
the daily changes of declination for the month of August 1841 resembles very 
nearly the curve of the same month in 1842, but the ordinates in the former 
year are much greater; in other words, the /aw according to which the sun 
produced the daily changes was the same in both years, but the force (repre- 
sented by the ordinates, the greatest of which is equal to the daily range) was 
not the same. On this account the daily range may be considered as the 
most important magnetic element ; and what is most likely to lead us to a dis- 
covery of the causes of magnetic phenomena is a careful investigation of the 
circumstances (probably meteorological) on which the daily range depends. 
Similar considerations apply to the secular changes, which present remarkable 
irregularities from one month to another; these irregularities (not the secular 
change itself ) are probably connected with the same or similar causes as the 
differences of the daily range. I intend, as I mentioned before, that the ob- 
servations of our establishment shall be for some years to come particularly 
directed to these points ; and I am inclined to suppose that a similar system, 
if followed in the British and colonial observatories, would prove not only in 
this, but also in other respects, beneficial to the magnetic inquiry. The dail 
work of magnetic observatories has been hitherto so considerable, that little 
time was afforded for different minute investigations, that nevertheless are of 
great importance for the final results. By diminishing the daily work as I 
have mentioned, ample time will be afforded for various investigations respect- 
ing instruments, methods and probable errors ; the different methods of deter- 
mining the absolute horizontal force and inclination may be tried and the 
results compared; the constants of the instruments may be determined by 
repeated experiments and the probable errors ascertained ; experiments may 
be made to determine the effects of the temperature and moisture of the air 
on the suspension, the difference between the temperature indicated by the 
thermometer of the bifilar and the true temperature of the bar, together with 
the corrections depending on this difference, &c. Besides, if the observations 
(which I would think it important to publish with as little delay as possible) 
should at any place show anomalies or peculiarities, new observations may be 
made to any extent that may seem necessary for obtaining a decisive result. 
These I believe are the considerations that may be urged for continuing all 
the magnetic establishments as they now are, but on a reduced scale. As to 
the question whether the present system of observations should be continued 
without alteration, I will simply express my opinion that I do not think it ad- 
visable, and will not attempt to give reasons for this opinion, because I believe 
I agree on this’ point with all those who have taken active part in the mag- 
netic inquiry. .- ; 
There is one point alluded to in the letter of the Committee on which I 
will add a few words; I mean the powerful influence which the example of 
the British government has had in promoting in other countries the important 
branch of science now under consideration. A general interest in the pro- 
gress of science, and, above all, a willingness evinced in almost every country 
to take part in scientific enterprises that seem to require general cooperation, 
may be considered as characteristic of the present time, at least the effects 
have not at any former period been so conspicuously manifested. A plan of 
great utility for science, if judiciously arranged and once realized to a certain 
extent, can scarcely fail to obtain not only the support of scientific men in 
