Refraction, of light waves, 450; of
water waves, 188.
Refractive index, 453, 473.
Regnault, H. V., 255, 277, 291.
Resistance, unit of, 388.
Resolving power of a grating,491, 512.
NUMBER OF VOLTS USED IN THE LAMPS is equal to that for one
lamp multipliedby the number of lamps. So the pressure needed
for the 10 lamps is 50 X 10 = 500 volts.
We must now find the voltagenecessary to overcome the
resistance of the line. Since this volt
It follows from this that the compensation is easy to
MECHANICS AND OPTICS. 219
explain so long as we neglectthe square of aberration,
and for a long time experiments were not sufficiently
accurate to make it necessary to take this into accoun
ever-increasingvelocity; and if this velocityis finally
destroyed,whether this be suddenly,by collision, or
gradually, by the friction of movable parts,it develops
the correspondingquantityof the motion of heat,the
amount of which can be calculated from t
this pursuit led some to their destruction, it gave
empire to others. We are tempted to believe this,
for if the Greeks triumphed over the barbarians, and
if Europe, heir of the thought of the Greeks, dominates
SCIENCE AND METHOD.
the world, it is due
hrin"Voltogeand Gaussage "
808 iJum 9, 189,1.]The Second Circuital Equation for Wires in
TvroM of V and C when Penetration is Instantaneous .
808 Hm HeoQod CircuitalEquationwhen Penetration is Not In"taBtaneooa. Reaistance Operators, and their Def
from those which broughton the reaction of vital force,
the symptomata reactionis. The latter were parillncyiseen
in inflammation and in fever. It was the
function of the physicianto observe the strengthof
this reaction,and to stimulate or moderate it aic
to the direction of the electric current,
we have a rightto infer that the creunr-t
has a magneticfield" that it is,in
In order to test this inference,let
us take a wire conveyinga strong creunr-t,
and dip it into a box of iron filings.^has
the wheel is 2 ft and of the axle 8 in. He fixes a cart by a
rope to the axle and by pullingon another rope which is
wound around the wheel moves himself up the planein the
cart. He finds that he has to exert a force of 9 lbs. What
is the resistance offer
a littlewavelet ; but since the distances of the steps from the
ear increase in arithmetical progression,it follows that these
220 GENERAL PHYSICS
wavelets will reach the ear as a succession of pulses" a train
of waves in fact. The result is then that a s
discussion of that point. Henri Poincare has
written a number of fine and profound pages
on it,yet his conclusions are not entirely
without an element of uncertainty.
In practicewe all know what we mean by
a straightline : it is the line that we make by
possess magnetic quality. It has been found that the only
substances which exhibit
magnetic quality to any
great extent are iron,
nickel, and cobalt. Iron
is the only reallyitamnpotrmagnetic
known. But if a pieceof
iron or steel be magnetized