The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1850-08-27

fioi shepard, Dr. jackson, and MI. brewer, IN
white zinc paint, and its advantages over white
lead, where there is sulphuretted hydrogen.
An analysis OF red mari, of Springfield, Mass, BY
| DR.. &. i. Jackson.
d. JACKSON showed specimens of wood painted
with this mari.
Mr. WELLS exhibited specimen of the mari it.
self, and described the process of manufacturing
it into paint. Further remarks were made upon
the subject by DIR. jackson and Prof Shepard
On the determination OF phosphoric acid, by T, 8.
Hunt. This communication Was accompanied by
remarks upon the analysis OF soils, with a state
ment OF results.
Or. JAcKsoN was glad to find that Mr.. Hunt had
succt eded in bringing the determination of phos-
phoric acid of soils TO such certainty and accuracy.
He believed the limits of barrenness and fertility in
soils re 81 within two per cent ia the OF certain
oftheir constituents, and then made some remarks
in reference 10 leached ashes as fertilizer
Mr.. Hunt thought the limit 10 lay between much
smaller limits than DIR. Jackson had stated
The subject of leached and uneached ashes was
further remarked upon in respect 70 their relative
value, by Mr.. s. w. Johnson, DIR. I. ;. Jackson
| and Prof. johnson.
| SECTION OF PHYSICS AND ACKNOWLEDGEMENTS
CURRENTS AND DISCHARGES.
On the law OF the induction of an elastric current
upon Itself, and OF eectnca discharges straight
wires. BY j. ii. Lane, American Patent Office,
Washington; presented by fr,iessor Olmsted.
| AbstIact:-
| currents, was made by Prof Faraday After his
| discovery, Prof Henry followed in very eabo-
rate series OF experiments in which he developed
some new and remarkable phe nomen ma, and brought
cut the most complete calculation OF the laws of
lie induction of electric currents that has been pro-
duced. He discovered the induction of a electric
current upon ITSELF and referred IL TO the general
principle OF inductive action at distance, as dis
covered by Faraday. The conductor OF current
was regarded as made up of an infinite number of
Infinitely small tibres, and the induction of the cur
tent upon itself more than the lnductive
orce exerted upon each fibre, by the currents ge-
Grated in all other ibres. My object in this COM
munication is, 10 present the principal results OF
mathematical investigation OF the laws OF the in
duction of a current upon ITSELF some account of
which was read before a meeting OF the National
Institute in Washington, some two or three months
since. The most material part Ut the fundamental
law, from which we must set out, has been pro-
posed by Prof. Henry, as deduction from his In
wstigation. They cannot, however, be regarded
as demonstrated by actual experiment, and If the
results here given, deductions from the m shall
furnish any of testing their TRUTH one object
OF the vestgaiion will have been obtained. The
fundamental law adoptedl as the bases of the In
vestigation, is ths:-The inducuve f9rse exerted
by a current generated in infinitely short ele-
ment of linear conductor at any given point lies, in
the plane OF the elementary current, In an opposite
direction 10 il, and at right angles To the
line of direction drawn from it to the given point,
and is directly proportional To the length OF the ele-
ments multiplied into the sine of the angle IL makes
with the line of direction, and nversely proportion
| al 10 the square of the distance. The lnductive
| force exered by current, generated In straight
| linear conductor of unlimited length is IN drec-
ton parallel TO the CONDUCTOR and In the inverse RATIO
simply Of the perpendicular distance from II. Inc
same is very nearly true with conductor OF Ii
mited length, for any point whose perpendicular
distance is small compared with the distance from
either exire nifty OF the conductor, the error being
emily small quantity of the third degree. In the
second place, II will be readily seen, that II a cur
rent Of electricity generated IN long straight
pusmsc conductor, IN such manner lhat .he rae
mass Of the conductor, the whole inductive force
exerted by the entire current would be greater IN
the central parts of the cross section Than at or near
the surface. In the of a cy lIndrcal conduc-
tor, the nductive force exerted AT the surface
would be equal TO that exerted at the centre as the
diameter of a circle 10 half its circumference. Al
the first instant of the application of an electro mo
tive force TO generate current in straight cylin-
| drical wire, we must expect that the Fate OF de-
| velopemept of the current will be more rapid IN
hbres situated near the surface, than IN the more
| central ones. The rate OF deyeOpement in any
ibres is inversely, as the length of the shortest
chord that can be drawn through that hbre, in the
| cross section Of the wires.
| In the case of discharge of machine electricity
through wire, there strong reasons Tor bellev-
| ing that the current in most places never reaches
| quantity sufficient TO make the resistance OF
| conduciion much felt, in COMPARISON with the inn
| mense electro-motive force concerned. The more
comprehensive formula, from which this law Is
| iakeD, leads TO some curious results III regard 10
| ,lectrical discharge. That which al once arrests
attention is the tendency Of the discharge TO the
| surface of the wire, presenting some analogy to
the distribution Of statica electricity But the dis
Il
surface; for, though the initial deyelopement would
become infinite at the very surface, yet the depth
| to which this extends is an inhnismai OF the
| second degree, that the discharge must be dis
tnbuied throughout the mass with large excess
near the surface.
Another interesting result is that, II tbs discharge
| were passed successfully through two wires, OF
different dismeters, placed end TO end, the induc-
ton Of the upon itself in the two wires, or
what might be termed the resistance 10 discharge,
would be directly As the length, and inversely as
tk. stsrA .xxar. tnzf. A.tf nj he
cross section. This, should Il be confirmed, would
appears like marked distinction between galvanc
| and machine electricity, were We unacquainted
| with the induction OF electric currents.
There was communication the method Of
| ascertainDg the velocity Of the galvanie current,
BY Orange Judd, Yale Analytical Laboratory.
Description OF new instrument for measuring
the aDg etcontained between the optic axis of crys
tails, and for goniometrical purposes; accom-
| panied by. the angles contained between the optic
sAis Of some American mcas. by W. L. Blake,
Mr.. Blake's instrument is designed to assist the
| min. raoeist IN examining the internal molecular
arrangement of minerals by polsrized light, and TO
combine with the instrument ell the requisites for
| neurological measurements. He uses light pola-
rized by reflection, and eye pieces OF tourma-
| line or calc spar, combined with lenses, by which
he 10 enabled TO reduce the size of the system OF
| colored rngs around the optic axis OF crystals
| thus enabling the observer To measure the inclina-
ton OF the optic axis in their plates Of micas Mr.
Blake also presented table Of the angles contained
between the optic axis Of several American micas,
from different localities, the angles varying from
| degrees TO 75i. The instrument was exhibited and
/ explained
4 Ma MACHINE.
/ machine was exhibited, designed for producing
uniform continuous motion, for vhich the name Of
1 the Sprpg Governor has been proposed. The ap-
| psratus was invented by the Messrs. Bond, Of
| Cambridge. IL consists Of a train Of wheels com
| municatiDg with flywheel, intermediate between
| which and the motive power Is dead beat scape-
| meat, connected with a half second pendulum.
1 hef he 4vVh. 81 nd
| the rest of the machinery is through spring The
elasticity OF the spring allows the motion Of the cir
cumference OF the escapement wheel 10 be arrested
stevery beat OF the pendulum, while the rest OF the
train continues moving. BY tbis means all changes
in the motive power are eiiectually controlled, anda
rotation perfectly continuous and uniform secured
/ in the 6y-wheel, 80 that the moving force may be
increased without affecting it's velocity.
| The principle may be applied to various forms