, 1872-11-01

Young's theory OF undulation supplied this
lack 1t had its root in-the world Of experience.
It .was suggested by the waves Of the sea and of
the air. In Illustration of this theory, Professor
Tyndall introduced experiments Of wonderful
beauty he explained waves by means Of the
diagrams on the blackboard, renafking that he
enyied the Lowell Institute that slate: for he
had none 80 good at home. He claimed that the
waves Of light possessed the sar1e characteris-
tics as those Of water; SO that tho vol known
became tho easy explanation of the almost un-
known. He performed some exceedingly pretty
experiments with maggnates, finging iron filings
magnet, and throwing the image upon the
screen. Then, On jarrinS the plate, the iron
filings we're seen to arrange themselves in beau-
tiful magnetic curves around the poles of the
magnet. They moved with slow, rhythmical
grace, as if to the law Of some haa anhsatd music
might be said to have spent his life in the con-
temptation Of these effects. You had got by
this time some idea Of polarity, aud OF the def
nito structure produced by its action on parti-
cles. ,>
8; this moleoule on molecule the form Of a
crystal is built up.. A solution Of sal-a1nmoniac
was poured upon the glass plate, and made to
eYaporate, the faithful screen reproducing, like
aome magic mirror, the whole performance.
Jack Frost himself never wrought devices more
crystals shot ont in every direction, and half
subdued clamor of delight filed the hall. This
was followed by an experiment with acetate OF
lead, decomposed by o current Of electricity.
On the screen you saw reflected the images OF
the poles Of the battery, immersed in the liquid.
Instantly, from one Of the wires, shot out Won
derful frond-Gke branches of most exquisite
shapes, only to fall away when the current was
reversed, while new shapes Of beauty lowered
about the other pole. These were the most
fascinating OF the numerous experiments Of the
evening. They were received by the philosoph-
ical With true scientific enthusiasm with de-
light eppreciative as well as edmiring. The
uninstructed portion Of the audience liked them
no less, and watched every shadow on the screen
with the Wide-eyed rapture OF children at 4
magic-lanteru show. There were various funny
little c0ntreten1ps, ae, when the Professor cried,
like Ajax, for light to his assistant, and the mis-
taken youth who managed the hall gas turned
on whole flood of it, and spoiled an expert
ment. ~ didn't mean you," the Professor
said, with funny twinkle in his eyes, end in
stantly we were in tho dark again. There is no
such thing as doing justice by description to
Prof. Tyndall's manner. It is so pleasant, so
coloqulal, so free from arrogance, 60 full of per-
sonal enthusiasm, as If the wonders he display
cd we're as new to him as the rest of us. He
makes science easy, coaxing his audience over
hard places by promises Of untold beauty to
come. In short, he is the very beau-ideal Of q
scientific lecturer The old men who 70, year
after year, to the Lowell Institute lectures, ap-
parently because the hall seems to them good
quiet place in which to take a nap, all keep
awake TO hear the lively Irish Englsdman, and
behold the beauties with which be feasts atten-
tive eyes. Nightly the throngs increase, and
critical and uncritical say of every last lecture
"This is the best, SO far"