Meetings of the Scientific Association of Great Britain. 59 
height, the velocity of their motion, ‘etc.,* enabled me to join in the 
novel discussion, and to call the attention of the observers to its im- 
portance. Mr. Herschel strongly supported the opinion, that the 
study of these meteers might be very useful, particularly m the de- 
termination of the longitude. Mr. Robinson, director of the observ- 
atory at Armagh, mentioned that he had already successfully avail- 
ed himself of this method of observation. 
A large part of the second meeting, was devoted to a subject of 
not less importance, especially in England; it was the question of 
the most advantageous form for vessels: this subject gave rise to a 
very varied discussion, in which Messrs. Lardner, Challis, Robinson, 
Bailly, etc., jomed. Some gentlemen spoke particularly of the in- 
adequacy of our analysis in the present state of the science, to pro- 
duce a solution of so complex a problem. 
Optics.—Optics occupied a large part of the next meeting, and 
we had the pleasure of hearing Messrs. Herschel, Brewster, Lloyd, 
Airy, Hamilton, Powell, Potter, &c., on this important subject. 
From the politeness of these gentlemen, and owing to the commu- 
nications, they were so good as to impart to me, I was enabled to 
profit by their researches, in preparing the notes which will be join- 
ed to the translation of Mr. Herschel’s treatise on light. 
Mr. Potter commenced by giving the results, to which he was led 
by his vestigations on the intensity of light reflected from the sur- 
face of bodies. ‘This philosopher has deduced from his observations, 
that when the reflection is from the surface of metals, and we take 
the sine of the angle of incidence of one hundred rays for the abscis- 
sa of a system of rectangular coordinates, the ordinate representing 
the reflected rays, is that of a straight line. ‘Thus in the equation, 
y=ax-+6, fora metallic mirror, y is the reflected light, a the trigono- 
metrical tangent of 355° 12/ b-=72.3 and w is the sine of the angle of 
incidence of 100 rays. When the reflection is from transparent bod- 
ies, the preceding equation becomes that of an hyperbola, and takes 
this form: (Sn eae ; 
a, 6, and ¢ are the constants which we 
* I was so fortunate as to converse with the illustrious Laplace, a few vee be- 
fore his death, on these investigations. This great philosopher remarked, ‘‘ We 
can assign the movements of the planets through space, we calculate the orbits of 
the comets, we determine after a short appearance their return, which only occurs 
at very distant intervals, and yet we have no precise idea of the nature of these 
meteors, which are constantly reappearing, and are only a few leagues distant.” 
Mr. Brandes is now repeating in Germany, the observations which he has al- 
ready made upon these meteors. 
