768 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS, 
[March 29, 13 . 3 
Cherry Brandy. 
Cherry Juice.15 gallons. 
Pure Rectified Spirits ... 20 „ 
-Simple Syrup.5 „ 
Oil of Bitter Almonds ... 1 drachm. 
Rectified spirit is understood to he whiskey, which has 
-been thoroughly deodorized by percolating through char¬ 
coal, and which is of first proof = 50 per cent, alcohol. 
Blackberry Brandy. 
Cherry Juice . . . 
Pure Rectified Spirits 
Simple Syrup . . 
dear Water . . 
Oil of Cinnamon . 
Oil of Cloves . . 
O 
O 
25 
5 
5 
1 
1 
gallons 
95 
drachm. 
The oils are to be first dissolved in about a pint of alco¬ 
hol , or high wine, and then to be mixed with the spirits 
before the addition of the other ingredients. 
PROFESSOR TYNDALL ON LIGHT * 
(Continued from p. 7 50.) 
In our last lecture we sought to familiarize our minds 
with the characteristics of wave-motion. We drew a 
clear distinction between the motion of the wave itself 
and the motion of its constituent particles. Passing 
through water-waves and air-waves, we prepared our 
minds for the conception of light propagated through 
the luminiferous ether. The analogy of sound will 
iix the -whole mechanism in your minds. Here we 
have a vibratory body which originates the wave-motion, 
we have, in the air, a vehicle which conveys it, and 
we have the auditory nerve which receives the 
impressions of the sonorous waves. In the case of 
light we have in the vibrating atoms of the luminous 
body the originators of the wave-motion, we have in 
the" ether its vehicle, while the optic nerve receives 
the impression of the luminiferous waves. We learned, 
also, that colour was the analogue of pitch, that the 
rapidity of atomic vibration augmented, and the length 
of the ether-waves decreased, in passing from the red 
to the blue end of the spectrum. The fruitful principle 
-of interference we also found applicable to the pheno¬ 
mena of light ; and we learned that, in consequence of 
the different lengths of the ether-waves, they were ex¬ 
tinguished by different thicknesses of transparent films, 
the particular thickness which quenched one colour glow¬ 
ing with the complementary ones. Thus the colours of 
thin plates were accounted for. 
But one of the objects of our last lecture, and that not 
the least important, was to illustrate the manner in 
which scientific theories are formed. They, in the first 
place, take their rise in the desire of the mind to pene¬ 
trate to the sources of phenomena. The desire has long 
been a part of human nature. It prompted Caesar to 
-say that he -would exchange his victories for a glimpse 
■ of the sources of the Nile ; it may be seen working in 
Lucretius; it impels Darwin to those daring specula¬ 
tions which of late years have so agitated the public 
mind. We have learned that in framing theories the 
imagination does not create, but that it expands, dimin¬ 
ishes, moulds and refines, as the case may be, materials 
•derived from the world of fact and observation. 
This is more evidently the case in a theory like that of 
lio-ht, where the motions of a subsensible medium, the 
ether, are presented to the mind. But no theory escapes 
-the condition. Newton took care not to incumber 
gravitation with unnecessary physical conceptions ; but 
we have reason to know that he indulged in them, 
* Abstract of a series of lectures delivered in the Cooper 
Institute, New York, and reported in the New York 
Tribune. 
though he did not connect them with his theory. But 
even the theory as it stands did not enter the mind as a 
revelation dissevered from the world of fact. The germ 
of the conception that the sun and planets are held 
together by a force of attraction is to be found in the 
fact that a magnet had been previously seen to attract 
iron. The notion of matter attracting matter came thus 
from without, not from within. 
The general facts of magnetism are most simply illus¬ 
trated by a magnetized bar of steel, commonly called a 
bar magnet. Placing such a magnet upright upon a 
table, and bringing a magnetic needle near its bottom, one 
end of the needle promptly retreats from the magnet, 
while the other as promptly approaches. The needle is 
held quivering there by some invisible influence exerted 
upon it. Raising the needle along the magnet, but still 
avoiding contact, the rapidity of its oscillations de¬ 
creases, because the force acting upon the needle becomes 
weaker. At the centre the oscillations cease. Above 
the centre the end which had been previously drawn to¬ 
ward the magnet retreats, and the opposite end ap¬ 
proaches. As we ascend higher, the oscillations become 
more violent, because the force becomes stronger. At 
the upper end of the magnet, as at the lower, the force 
reaches a maximum, but all the lower half of the magnet 
attracts one end of the needle, while all the upper 
half attracts the opposite end. This doubleness of the 
magnetic force is called polarity, and the points near the 
ends of the magnet in which the forces seem concentrated 
are called its poles. 
What, then, will occur if we break this magnet in two 
at the centre ? Will each of the separate halves act as it 
did when it formed part of the whole magnet ? No ; 
each half is in itself a perfect magnet, possessing two 
poles. This may be proved by breaking something of 
less value than the magnet—the steel of a lady’s stays 
for example, hardened and magnetized. It acts like the 
magnet. When broken, each half acts like the whole ; 
and when these parts are again broken, we have still 
the perfect magnet, possessing, as in the first instance, 
two poles. Push your breaking to its utmost limit ; you 
will be driven to prolong your vision beyond that limit, 
and to contemplate this thing that we call magnetic 
polarity as resident in the ultimate particles of the 
magnet. Each atom is endowed with this polar force. 
Like all other forces, this force of magnetism is amen¬ 
able to mechanical laws ; and knowing the direction and 
magnitude of the force, we can predict its action. Plac¬ 
ing a small magnetic needle near a bar magnet, it takes 
up a determinate position. That position might be de¬ 
duced theoretically from the mutual action of the poles. 
Moving the needle round the magnet, for each point of 
the surrounding space the needle takes a definite direc¬ 
tion and no other. A needle of iron will answer as 
well as the magnetic needle; for the needle of iron is 
magnetized by the magnet, and acts exactly like a 
needle independently magnetized. If we place two or 
more rods of iron near the magnet, the action becomes 
more complex, for then the iron needles are not only 
acted upon by the magnet, but they act upon each other. 
And if we pass to smaller masses of iron—to iron filings, 
for example—we find that they act substantially as the 
needles, arranging themselves in definite forms, in obedience 
to the magnetic action. 
Placing a sheet of paper or glass over this bar magnet 
and showering iron filings upon the paper, I notice a 
tendency of the filings to arrange themselves in deter¬ 
minate lines. They cannot freely follow this tendency, 
for they are hampered by the friction against the paper. 
I help them by tapping the paper ; each tap releases 
them for a moment, and enables them to follow their 
bias. 
The aspect of these curves so fascinated Earaday that 
the greater portion of his intellectual life was devoted to 
pondering over them. He invested'*bhe space through 
which they run with a kind of materiality ; and the pro- 
