36 
POPULAE SOIEKCE ]S:EWS. 
[March, 1891. 
law of coincidence. 'ITiirteen persons at table co- 
incides with the unlucliy number at the memora- 
ble supper in which Judas betrayed the sinless 
one and went to his own death. Spilling salt is 
coincident with the evils that accrued to the salt- 
tax gatherers during the French Revolution. The 
strangest part of these coincidences — which, if 
observed until sufficient data is collected, may be 
termed analogies — is, that there seems to be a cer- 
tain unexplained law of the mind in its groping 
that often leads to new facts and discoveries. 
In his Budget of Paradoxes, De Morgan relates 
the following story or theory : "The late Baron 
Zach received a letter from Pons, a successful 
finder of comets, complaining that for a certain 
period he had found no comets, though he had 
searched diligently. Zach, a man of much sly 
humor, told him that no spots had been seen on 
the sun for the same length of time, — which was 
true, — and assured him that when the spots came 
back the comets would come with them. Some 
time after, he got a letter from Pons, who in- 
formed him with great satisfaction that he was 
quite right; that very large spots had appeared 
on the sun, and that he liad found a comet soon 
after." To make the story complete there should 
now be found a connection between the comets 
and the sun's spots. The curious thing is that 
just this paradox was maintained before the Royal 
Astronomical Society by Professor Ashe before 
De Morgan's book came out. 
I have known one who has the capacity for in- 
vention to make statements about the necessary 
mechanical appliances needed to produce certain 
ends, that sounded wildly improbable; and yet 
the most improbable are now facts. The quad- 
ruplex system for use in telegraphy was dreamed 
of when to relate the dream was a tale of wild 
improbability. This has occurred many times, 
and allows a perfectly natural interpretation, — as 
some other mind traversed the same road and 
solved his dream into practicability by creating 
the necessary steel and iron image to express an 
embodiment of his thought. 
Again, there have been well-attested instances 
in which mind acts on mind independently of dis- 
tances. It would be hard to prove that when we 
think — and that in spite of a determination to 
think of other things — of some absent person that 
he is thinking of us. But if in a number of in- 
stances a number of persons were to record such 
experiences and compare results, the law of coin- 
cidence would have great weight in determining 
the truth or fallacy of such a law. In trying to 
grasp an abstruse subject like the relation between 
mind and matter, there must, from the nature of 
the working medium, ever be many opportunities 
for fallacious reasoning, — as it is impossible to 
speak of mind as affiliated with the body, with a 
brain and the nerve currents, without localizing 
the mind, and proving its habitat and absolute 
identity. Mental and bodily states are never 
identical, but contrasted. There is no means of 
affecting a compromise between them, and in try- 
ing to express thought about mind it is not easy 
to say anything without localizing it. There is 
the old difficulty to be met: Is mind found in 
every organ, or all in the whole? 
Leaving all this, however, and allowing the 
statement that mind is, indeed, as a phenomenon 
diff"erent from physical forces, but correlates more 
or less directly in strict proportion with these, 
mind must be admitted into the circle of corre- 
lated force. Of course it is quite impossible to 
reduce the quantity or quality of mind force to 
any method of mathematical precision. Vitality, 
energy, mental qualifications, health, courage, 
love, irascibility, may have a standard in our own 
mind with regard to an individual, but we cannot 
reduce such qualities with mathematical precision, 
and cannot communicate to others with exactness 
our own idea. When taking into consideration 
the physical facts underlying the mental facts, it 
may show that widespread concomitant action of 
the nerve currents and the agitation of the brain 
that may account for many of the unexplained 
incidents, divinations, witchcrafts, and similar 
phenomena as a result of that tumultuous con- 
flict, and exercise of energy in reconciling the 
union of the material to the immaterial, even 
among the inferior races of mankind. 
HINTS FOR EXPERIMENTERS. 
EXPERIMENTAL MAGNETIC NEEDLES. 
Foe electrical and magnetic experiments, ama- 
teurs sometimes find it desirable to mount mag- 
netic needles on rigid bearings, and without the 
aid of untwisted silk or other suspending fibres. 
The accompanying figure illustrates a method by 
which magnetized sewing-needles may be mount- 
ed in that manner. The needle (N S) is passed 
through the small card (0) at right angles to the 
needle (H). TTiis supporting needle is held in a 
vertical position by a very small glass cup (G) 
and by a glass tube (T). The small glass cup is 
formed by holding one end of a tube of 1-16 inch 
bore in the flame of a Bunsen burner until the end 
has closed itself and has assumed the shape shown 
I 
■fe 
niiT 
in the figure. During this operation the tube 
should be kept turning constantly, so as to heat 
the glass evenly. When the glass has become 
cool, the closed end is cut off" and mounted in a 
snugly-fitting hole bored in the wooden base (P). 
The support (T) is made from a glass tube by 
heating it and drawing it out into two tubes, each 
ending in a point of very thin glass. The end of 
one of these tubes is broken off' at a point where 
the opening so formed will just admit the blunt 
end of the needle (H). This tube may be mounted 
in a hole passing through a horizontal wooden 
support. The card (C) should be as small and 
light as possible, and the vertical needle should 
pass through its center. An astatic needle mount- 
ed in this way is shown at K. As may be seen, 
these needles are not supported exactly at their 
centers, and are otherwise unsuitable for electrical 
measurements; but they answer very well for 
many of the simple experiments which illustrate 
laws of electricity and magnetism. — Langton 
Byllesby. [Originalin Popular Science News.] 
THE CARTESIAN DIVER. 
For experiments with the Cartesian diver, I use 
a large flat bottle and a small vial, such as is used 
for homeopathic medicines. I completely fill the 
bottle with water. I then fill the vial about half 
full, a few trials determining exactly how much 
to use, and invert it in the bottle. The bottle is 
then corked, the cork being put in with more and 
more of force, followed by repeated careful loos- 
enings of it, until the vial barely floats. ITien, 
taking hold of the bottle and pressing the sides, 
the volume is decreased, and the vial descends, 
rising again when the pressure is removed. This 
method of showing the transmission of pressure 
is not new, but I think it is not generally known. 
I believe, however, that the following modifica- 
tion of the experiment is original with myself: 
Having corked the bottle so that the vial will 
barely descend, and remain at the bottom, I find 
that pinching the flat bottle edgewise, instead of 
flatwise, increases the volume of the bottle enough 
to cause the vial to rise to the top. The force re- 
quired in this latter case is, of course, greater 
than that required in the former. One who has 
never used this simple apparatus will be aston- 
ished at the remarkable' sensitiveness to pressure 
which may be obtained.— Clarence M. Bou- 
TELLE, in Scientific American. 
TEST PAPER FOR ACIDS. 
Cut white filtering paper of neutral reaction in 
pieces of about six inches square, and impregnate 
them with tincture of curcuma (1 part curcuma, 7 
parts alcohol, and 1 part water). Place the paper 
on threads to dry. When dry pass a sheet of it 
through a bath composed of 40 drops of liquor 
potassa) and 100 c. c. water. Then immediately 
pass it through a bath of water, — flat earthen 
dishes are convenient for the baths, — and at once 
place it on a thread to dry. As soon as it is dry 
cut it in pieces and inclose them in tinfoil. The 
paper will not bear long exposure to light and air, 
but will keep well if inclosed in tinfoil. It is 
much more sensitive than litmus paper, and will 
detect acid in a mixture of 1 part of hydrochloric 
acid in 150,000 parts of distilled water, and will 
detect carbonic acid in spring water. If the wate^ 
be boiled to expel carbonic acid, and a yellow 
color is produced, some free acid (besides CO,) is 
shown to be present. The best way to use the 
paper is to touch it with a glass rod which has 
been wetted with the liquid to be tested. The 
paper can be freshly prepared in fifteen or twenty 
minutes. — S. J. Hinsdale, in American Druggist. 
»♦* 
SCIENTIFIC BREVITIES. 
On Prout's Hypothesis with Reference to 
THE Atomic Weights of Oxygen and Carbon. 
— On comparing the formulae of different com- 
pounds which only contain hydrogen, oxygen, 
and carbon, J. A. Groshans concludes that the 
figures 12 and 16 must be admitted for carbon 
and hydrogen. 
Mr. Berthelot has proved by experiments 
that there is no foundation for the belief that the 
earth absorbs and retains more carbonic oxide 
than other gases — an hypothesis offered to ex- 
plain several cases of asphyxiation which have 
occurred when miners went into a level shortly 
after an explosion. 
The Name of the Kangaroo. — At a recent 
meeting of the Linnean Society of New South 
Wales, some discussion took place as to the mean- 
ing of the now universally accepted term kanga- 
roo. It appears that it has been reported that in 
the language of the natives of the Endeavour River 
region the word kangaroo means "I don't know." 
This answer was given to Captain Cook m reply 
