The sun., 1897-02-07

with the present plague situation In India IL the
approaching annual pilgrimage to Mecca. This
gathering Of the faithful-the most ignorant
and the most dirty OF the fsithful-is. as is we'll
known, the most dangerous event OF the year
from n sanitary point OF view. And yet Its ar
bitrary prohibition would be q delicate and
most dangerous undertaking. The faith Of
as one writer points ont. in tho
divine Importance attaching to a pilgrimage
to tho holy shrine OF the Prophet, and to
tho coveted title Of "Haji" which follows
It, is blindly strong and fanatical; they
believe, indeed, that the more difficulty en-
and the more devastation created.
the moro In proportion nre tho divine blessings
to bc realized. To tell some would-be Halls"
that their pilgrimage to Mecca is likely to
spread death throughout non Mob medsn
countries is to make them the more eager and
determined to undertake it, since. In the opinion
of the more ignorant, the Great PROPHETS
prophecy can only be consummated by the
annlhilation Of all the "unfaithful"
Tho cooperation OF the Sultan. OF the Shah.
and OF the Amcer Of Afrhanistan would be al
most essential to the successful prohibition Of
the Mecca pilgrimage. and It is extremely
doubtful II this could be obtained even by strong
diplomatic pressure. The attempt will probably
be made. however.
Prof. Dewar made announcement at the
Royal Institution on Friday last Of some OF tho
results OF his past seasons experiments with
liquid oxygen and other low temperature In
vestirations. Some OF his deductions are OF alb
rorblng scientific and popular interest The
temperature Of liquid oxygen. no explained, Is
constant at 1899 Centierads below zero. The
unscientifc mind naturally asks how II is pos
sible to measure such incredible cold as these
a. Eu.l
stance, that 1t is difficult. IL not impossible. TO
measure ordinary atmospheric temperature
even with q spirit thermometer when 1t falls
to minus 50' Fair. or lower. Prof. Dewar
pointed out two or three methods. The most
remarkable 10 by means OF thermo-
electric diagram prepared by Lord Kelvin and
Prof. Talt. IL has been found that. taking ad-
vantage OF = recently discovered law of nature.
extremely low temperatures may be measured
by observations OF high ones. There 10 an elec-
tric balance. roughly speaking. between a tenn
peraturo 1000 above freezing. for instance. and
one l00' below freezing. The temperature Of
liquid oxygen may be determined by immersing
ono mo.elcctric junction in n substance
which is boiling at the temperature 1899 Cont
grade above zero. t. C.. freezing. and another In
liquid oxygen itself. The two currents which
are produced exactly balance each other.
Prof. Dewar performed an interesting expert
ment to show the answer to q question often
asked him. namely: suppose the earth were to
be cooled TO tho Temperature OF space, what
would be the depth Of the ocean Of liquid air TO
which the present atmosphere would DO re-
duced ? The homogeneous atmosphere OF tho
earth. Prof. Dewar explained. was su pposed to
be equal to an envelope OF air as We know 1t
about Ave miles In thickness. Ir the lecture
room. where the professor was speaking. hung
. tube 90 feet long. that is to say, 1t was
about l-500th part as long rs the atmos phero
was high. II this tube were cooled 50 rs to lque-
~ the air In II the amount OF liquid prod uced,
IL multiplied by 500. would give tho thick ness
Of tho ocean OF ilouefed air that would spread
over the earth In the circumstances suggested.
The experiment was tried, with the result that
liquid air to the depth OF about 81 OF an inch
accumulated ct the bottom Of the tube. In
other words, when the earth freezes and all
forms OF life disappear. there will float above
the present ocean OF water. long since changed
to Ice. an ocean OF liquid air th!rty-threo feet
deep on the average.
Prof. Dewar, referring to the osmotc action
OF gaseous oxygen. proceeded to inquire whether
the same action was observable at low temp mpera-
lures, but said he was unable to ind that liquid
oxygen was able to wet or permeate n film Of
India rubber. Turning to some OF the optical
prOpcrtles OIL oxygen nc NpOke Ol tuo seen
at sunrise and sunset In the solar spectrum.
These originated In our Atmos sphere, and some
OF tho most characteristic OF them were pro-
duced by oxygen. From the top Of Mont
Blanc some OF them were not TO be seen because
the OF ygen OF the air did not make up 81 ficent
thickness to effect the absor rption. and In the
clear air OF the Sahara they appeared with q
particular elevation OF the sun. Tn, same effects
could be Initiated by passing light through
oxygen at various pressures. and. more than
that. liquid oxygen of equivalent thickness
would show the same bands. 1t was remark able
that the same absorption was to be found when
the substance was at high temperature as n
gas. when II was liquid, aud when II WAS at
the lowest temperatures. Oxygen, again, was re-
Inarkable as an element that was magnetic rs a
gas, As q liquid. and perhaps as solid. The
measurements, particularly tho accurate
measurements which alone were valued In
those days. OF the various constants OF liquid
oxygen were exceedingly intricate and labori-
Gus. However. DR.. Fleming and himself had
succeeded in determining the values OF several.
such as its magnetc permeablity and suscepti-
bility, &c. Its magnetic properties were Illus
trated by q striking experiment. A ball mag
netic in air was shown to be apparently diamag.
netic when immersed In liquid oxygen. In air a
magnet attracted Il, In the liquid tho same
magnet repelled II.
The military use OF bicycles is 4 subject re-
ceiving an astonishing amount Of attention just
now In Continental war Offices. Germany and
France are I'll, most active rivals In the compe-
tition and some Of the experiments which have
recently been undertaken would seom absurd IA
all except bicycle enthusiasts OF the EXTREMIST
type. Imagine. for instance, equlpping the In
fantry OF an army corps with bicycles! And