New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1850-08-20

copied to vsit the residences Of NJ. Salisbury,
Prof c. y. Shepard, md the Mayor Of the city, re-
spectvely, on Tuesday Wednesday and rn1rsiay
evenings Of this week.
An Invitation has also been EXTENDED 20 the As
IocistOn, by the Trustees Of Amherst College, -
hold it next Annual Session az A nherst- STINT
Ter invitation is also rendered by Prof Mitchell or
behalf Of Cincinnati The mater has beenrsierred
~ the Standing COMMITTEE without dehoite acton.
The mem bers are met by the gre Atest cordially,
and most friendly greetings and vii no douo' have
al abundance Of pleasure and 'lionizDs before ne
Convention is ended. They are sill pouring IL ~
every train.
The Hrst paper read was by Pro- OLssrLD, upon
CERTAIN POINTS or ELECTRICAL THEORY.
This was an interesting paper though upon
subject u ith which all are more or lets familiar
Prof Olmsted stated that be bad ifon time 70 time
made various memoranda on certain sab scts cor
nected with the theory or practical aPPl ;atons OF
Electricity, from which he would select few
points for hi, present paper BE proceeded 20 con.
alder them under FIVE distinct heads-viz lst,
Phenouens produced by the expansion Of air 81,
The effect OF msss in connection with : c)nt1cti1g
surface 80, The division OF one electric charge
between different conductors 4th, The returnDg
itroke 5tb, Trees struck by lightning.
The Professor illustrated the first division OF his
subject In reference 10 the expansion OF cir conse-
tmples where buildings had been struck by light
ming. In the year lS4] house vas struck 10 the
Eastern part Of the City Of New Haven where
the effect IN queItion first attracted Prof d. atten.
uoD. The house had no lightning rod, bu. the chin
ney which rose from the center Of the roof was the
point OF attack. A small fire was b1rning IN q
fireplace in the family room, the smoke Of Which
undoubtedly invited the charge in that direction
The lightning made IT. way TO the earth outside
but fact Of more interest was the indication In the
family room Of certain effects which we're evident
y due 70 tho sudden and powerful expansion Oithe
air Of The Chimney, and ofthe apartment be.OF.-
The ashcshDd embers tina. were ia the fireplace
were blown out and scattered, the Windows op.
posite singusry broken, and there we're general
evidences Of the action Of elastic force pressing
uniformly from within. The Professor has since
observed a nun Der OF instances where similar indi.
cations were afforded OF sudden and violent ex-
paDslcn Of the internal air May We not, he asked,
refer 70 this cause some Of those where heavy
bodies IRE moved out Of their places by stroks Of
lightning
Regarding the effects OF mas in connection with
a conducting surface, the Professor held that It
has been abundantly shown tha, the conducting
power OF the ishtDjngrOd Is greatly affected By
the nature Of the masI, independently Of the sur
face, upon which sons many have been induced to
rely for protection without though. Ito the IL
OF the interior structure IL may be justly IN
feued thas sand by being wet is still bat al inQer
feet conductor and tina; hence lightning rod which
terminates in a sandy soil has bat an Indifferent
position even when the sand Is moist la siciouI
soil, therefore, it Is peculiarly important that the
bottom OF the rod should be ia communication vita
some better medium than the DO itself-such as a
well an aqueduct an iron railway, or an iron fence.
AS TO the division Of the electria charge between
different conductors, Prof D. has bad opportunities
OF observing this fac! learned by Prof Henry, that
EVEN the beat constructed rod, when Transmitting
heavy charges Of. electricity, readily parts with p0r
tonB Of the charge TO nelghOOnDg cond acIOrs-
Several instances were related. Daring the
season al thunder-itoTmI the Kitchen chimney
has usually FIRE in il, and is the only one Of toe
building that hiss fire; and hence requires special
projections nor ought il to be cons dered as July
protected BY = neighooriDg rod. la one nstaac5
cited by Prot. o. when a heavy stroke OF lightning
struck the chimney Of 4 house, the charge seemed
TO descend unbrOkcn % the garrett hoor, and there
TO divide itself into fOu. streams, each pursuing
different route to the earth, and each Stroag
enough 10 leave pRpsble trsces Of It's path The
City Of New Haven was considered as one 81 those
places peculiarly liable 20 be stfuck with lightning
Seldom does {, year pass, said the Professor, win
out serious damage BY lightning % one %. more
buildings and in lsi5, no less than seven dSe'liog
houses were struck, five Of them with much vi)
lerce. Three OF the number were armed with
lightning rods which evidently trausmitted tbs
greatest AIT Of the charge, and probably were tle
means Of preserving the lives Of the inmates the
reason WY New maven IS peCllaGy HAD.e . a..
tack from lightning WIS given as consisting In The
nature Of tho sci, which is highly adiciolI, AL
consequently in the dry weather tat uIaily pre-.
walls N the season Of thunder storms il presents %
the conductor a highly resisting medium. Snail
bodies Of water, n sp0tI hAbtually damp, were
shoNn b invite an electric discharge.
Some further interesting observations on The re
turning stroke and trees struck by lightning, wi.h
a curious discussion which SprAng up from iho la,
ter topic | an compelled TO leave for another d.
patch, as the Last train is leaving. ! shall resume
the narrative in ny next. q.