132 
POPULAR SCIENCE NEWS. 
[September, 1890. 
very unlikely, for the difficulty of escape experienced 
by an insect that visits the flower, and also the fact 
that it is only those insects that encounter great 
difficulty that can remove the pollen — these points 
make it plain that fertilization by insects will not 
account for its increase, for although Darwin has 
beautifully described tlie entrance and exit of an 
insect to this flower, yet that same insect, though 
traced, has not been seen to enter the same plant 
or another. It takes for its motto "Once bit, 
twice shy." It remembers its struggles to get out 
and naturally' avoids the plant. 
Most of you are doubtless familiar with the 
flower, which has a large labellum, whose edges are 
incurved on its upper surface, forming an orifice, 
and a tempting one to insects. This gives it the 
appearance of a slipper, and hence its common 
name, lady's-slipper, or, as the Latin name implies, 
Venus's slipper. Now what takes place when a 
small bee enters the labellum, which is parti}' closed 
by the stigma.' The bee enters easily, but the 
inflected edges of the labellum prevent it from 
returning that way unless it is a smallish insect; 
but in that case it would have taken no pollen with 
it wherewith to impregnate the stigma, for it would 
have been nowhere near the pollen. No ; after vain 
efforts to return the same way the moderate sized 
bee very naturally turns his attention to other 
chances of egress, and this is generally found by 
one of the two small elastic orifices close to the 
anthers, and in escaping it must inevitably carry 
off some of the glutinous pollen (for in this genus 
the pollen grains are not in dry masses as is usual, 
but are coated all over with a viscid fluid.) 
This being done it is evident that unless that 
insect revisits the same flower or another the stigma 
cannot be fertilized. Deaths in the labellum are 
numerous, consisting of insects of too large a size 
to escape by the anther orifices and unable to crawl 
up the sides of the labellum, which are covered by 
reversed hairs, or else by small insects which are 
held with a tight grip by the very sticky pollen. 
There is no nectar, and hence it would seem as 
if the motive for a visit was curiosity, emphasized, 
my pharmaceutical tutor used to say, by the fact 
that all the corpses were of the female sex, but I 
fancy this was one of his regular little jokes to 
tickle up the interest of a class of students. 
Insects experiencing the above difficulty and 
escaping, generally very quickly desert the locality 
in which the plants grow. 
That cross fertilization takes place is extremely 
improbable, owing to the above remembrance' of 
prison life by the insect, and there seems to be no 
record of anyone having seen an insect visit a 
cypripedium having pollen attached to his back. 
When small insects, up to the size of a little ant, 
crawl right through the labellum and out at the 
anther orifices, they do not take the pollen off at all, 
for the distance between the part of the labellum on 
which they tread and the pollen masses is too great, 
being one-eighth to three-sixteenths of an inch. 
Small bees and certain wasps are of the size to 
remove the pollen grains, but if you place one 
of such in the labellum and watch, you will find that 
although they generally escape besmeared in pollen 
by the anther orifices, yet the insect will have gone 
through such a laborious work that it seems hard 
to believe that any insect would enter such a trap 
again. The plant spreads rapidly on the continent, 
and it seems as if it must be able to reproduce 
itself by the roots. 
Cephalanthera grandiflora is fertilized in the bud 
state by the pollen grain emitting tubes into the 
stigma ; but construction makes this unlikely in the 
case of Cypripedium. — Wm. Baxter, in Pharma- 
ceutical Journal. 
THE STAR MIZAR. 
Every observer of the heavens, who knows by 
name some of the brightest stars, is familiar with 
the constellation called the Great Dipper, visible in 
the northern sky through the whole night and 
throughout the year. It consists of seven stars, 
four in the bowl and three in the handle. An inter- 
esting discovery has recently been made by Prof 
Pickering, of the Harvard University observatory, 
concerning one of the stars of this beautiful group. 
Mizar is the name of the star. It is the middle star 
in the handle, is of the second magnitude, and has 
attracted much attention ever since men began to 
study the stars, because even to the naked eye it is 
double. It has a companion, Alcor, plainly visible 
to observers endowed with good visual power. 
Alcor is of the fifth magnitude, and is about 11' dis- 
tant from Mizar. The tiny star seems to be growing 
brighter, for the Arabians considered it a severe 
naked eye test, and it is now comparatively easy to 
detect. The telescope shows plainly that Mizar is a 
double star, its components being of the third and 
fifth magnitudes, the one a brilliant white, the other 
a pale emerald. The marvellous discovery is now 
made that the larger star of the pair is also double, 
the two stars that compose it being so close together 
that the telescope cannot separate them. The spec- 
trum of a star, like tlie solar spectrum, consists 
of the seven primary colors, crossed by dark lines. 
These lines form a kind of astronomical alphabet. 
If the star is coming toward us, they shift toward 
the violet end of the spectrum. If the star is 
receding, they shift toward the red end. Two stars 
very near together, having the same spectrum, can- 
not be distinguished from a single star as long as 
they are at rest. If they revolve round each other 
in a plane inclined to the line of sight, the lines 
of their spectra will be single when the stars are in 
conjunction, and double when they are at elonga- 
tion. This is the case with Mizar, and the doubling 
occurs at intervals of fifty-two days. Prof. Picker- 
ng, therefore , infers that these two stars are 
immense suns revolving round each other. He 
lestimates that the period of revolution of each sun 
about the common centre of gravity is one hundred 
and four days, and that the maximum velocity is 
one hundred miles a second. These conclusions 
are the result of measurements of almost incon" 
ceivable delicacy. — Youth's Companion. 
SCIENTIFIC BREVITIES. 
The Khojak Pass, pierced by the recently-com- 
pleted tunnel, is 7,500 feet above the sea, and about 
2,000 feet above the level of the surrounding country. 
The tunnel pierces the range at right angles, and its 
course is, therefore, due east and west, and it enters 
the hill about 1,000 feet below the crest of the pass. 
The length of the tunnel is 12,600 feet, or two and a 
half miles, approximately, and it will carry a double 
line of rails. 
To Cut Large Glass Tubes. — The process 
of cutting glass tubes by electricity appears to have 
met with success. The tube is surrounded with fine 
wires, and the extremities of the latter are put 
in communication with a source of electricity, it 
being also necessary, of course, that the wire 
adheres closely to the glass. When a current 
is passed through the wire the latter becomes red- 
hot, heating the glass beneath it, and a single drop 
of water deposited on the heated place will cause a 
clean breakage of the glass at that point. Contrary 
to what takes place in the usual processes of treating 
this material, it is found that the thicker the sides 
of the tube, the more successful is the operation 
likely to be. 
Practical Cljen^istry aijd tlje ^rts. 
SOME UNCOMMON BUT USEFUL 
METALS. 
There are quite a number of metals which 
are very sparingly distributed over the earth, 
and which few people have ever seen, but 
which have some exceedingly useful applica- 
tions in the arts, and, in small quantities, are 
in almost constant use. 
Hydrogen, the lightest of all the elements, 
was discovered by Cavendish in 1766, and is 
considered by the best authorities to be a 
gaseous metal, just as inercury is a liquid 
metal at ordinary temperatures. Very few 
persons have ever seen solid hydrogen. 
Mercury becomes solid at — 40°, but, accord- 
ing to Professor Pictet, hydrogen gas requires 
a temperature of — 140°, and pressure of over 
two tons to the square inch, before it liquefies 
even. By suddenly removing the pressure 
from this liquefied hydrogen, the cold pro- 
duced by its evaporation is so great that a 
part of it solidifies into a state resembling 
metallic grains, which remains visible for 
several minutes. Its metallic nature is also 
rendered probable by its directly uniting with 
a metal resembling platinum, and known as 
palladium, to form a sort of alloy. The 
weight of a single molecule of hydrogen has 
been calculated not to be greater than one 
ten thousand millionth of a gramme, and a 
cubic centimetre of the gas contains at least 
twenty-one trillions of such molecules. Al- 
though these figures are quite incomprehensi- 
ble to the human mind, they must be approx- 
imately correct, and represent actual and 
existing magnitudes. 
Lithium is a quite rare mineral, which 
occurs in some varieties of mica, and also in 
small quantities in the waters of certain min- 
eral springs. It is considered to possess a 
distinct medicinal value by some physicians, 
and is probably taken into the system, at least, 
as we have detected it by spectroscopic analy- 
sis in the blood of a person who had been 
drinking a strong lithia water. 
Barium is a metal closely allied to calcium, 
the metallic base of lime. It is never used in 
the metallic state, but the sulphate of barium 
is quite extensively used — either honestly or 
dishonestly — as a substitute for white lead in 
paint. It is cheaper than white lead, and 
is not changed in color by the sulphur com- 
pounds often present in the air, but possesses 
less covering power than lead, and is less 
permanent in other ways. The peroxide 
of barium is used in the preparation of per- 
oxide of hydrogen, and the phosphorescent 
sulphide of barium is a constituent of some 
varieties of luminous paints. The green fire 
used in pyrotechny is also due to the presence 
of this metal in the form of a nitrate. 
Strontium, which is, chemically speaking, 
the brother of barium, is even more rare, but 
