TRANSACTIONS OF THE SECTIONS. 13 
on this point, we have it in our power not only to increase our own observations, but 
also to solicit the aid of others, that in the re-observation of an object the want of 
confirmatory evidence may not exist to occasion a doubt as to the certainty of 
what is recorded. Webb says very truly (Celestial Objects, second edition, p. 68), 
we are scarcely as yet possessed of the means of detecting small changes. The 
evidence capable of being brought to bear on the question of change is consequently 
very limited in extent, especially as former records are more or less open to be regarded 
as inexact drawings or inaccurate statements when they happen to differ from pre- 
sent observed appearances, still as instances such as are given above zncrease, and they 
are upon the increase, it will become more and more difficult to put aside the 
earlier records. It therefore remains rather, as recommended by M. de Beaumont, 
to increase our observations and compare them with the earlier records than to rest 
satisfied with the notion that, as no change has been satisfactorily ascertained, it is 
unlikely upon certain theoretical considerations that we may meet with any. 
The Meteor Shower of August 1868. By Groner Forses. 
The author merely stated the results of some observations made on this shower 
on the nights of the 10th—11th and 11th-12th of August last. The peculiarities of 
this shower were for the most part the same as last year. The hourly average 
number on the first night was 21 on a clear night seen by one person, while last 
year the number was 25 on a hazy night by the same person. The radiant-point 
was approximately R.A. 2" 16" N.P.D 31°. Last year it was nearly the same. 
Two meteors traced curves, one of them of a very remarkable form. When a 
distinct train was left the meteor was generally noticed to pass beyond the end of 
the train and to become suddenly extinguished without previous diminution of bril- 
liancy. No trace of the radiant discovered last year in Pisces was noticed. The 
average size of meteors was that of a 4th magnitude star. 
ACOUSTICS. 
On a Simple Method of exhibiting the Combination of Rectangular Vibrations*. 
By W. Frercner Barrett. 
Physicists are well acquainted with the elegant experiments of M. Lissajous, in 
which the vibrations of two tuning-forks, placed at rectangles, are optically com- 
bined by viewing a ray of light successively reflected from a mirror attached to 
each fork. A regular series of curves is thus obtained which gives a perfect 
optical expression of each of the musical intervals, the curves augmenting in com- 
plexity as the dissonance between the forks increases. 
Instructive and beautiful as are these experiments, the extreme costliness of the 
apparatus necessary for their proper exhibition has hiherto debarred many from 
repeating them. 
wards of two years ago the author found a method of obtaining any desired 
combination by an extremely simple arrangement. A piece of straightened steel 
wire, about No. 16 gauge and some 12 or 18 inches long, is first well softened in a 
flame at a point 6 or 8 inches from the end, which length is then bent downwards. 
The extremity of the longer portion is fixed in a vice, a silvered bead is cemented 
by marine glue on to the summit of the bend, and the instrument is complete. 
The whole system is thrown into vibration by smartly tapping the wire near the 
point held in the vice, and i a direction oblique to the plane of the two wires. The 
vibration travels up the wire, rounds the bend, and throws the inclined arm into 
motion. The latter, being free, vibrates more easily than the portion which is 
fixed at one extremity ; a compound motion is thus the result, and the spot of 
light, reflected from the bead, describes a curve expressing the resultant action. 
The ratio between the vibrations of the two parts of the wire can evidently be 
adjusted, or altered, by raising or lowering the point clamped in the vice. The 
same end may also be obtained by loading the free portion of the wire by a little 
* Published iz extenso in the Philosophical Magazine for September 1868. 
