New-York tribune. [volume] (New-York [N.Y.]) 1841-1842, 1841-12-18
DR.. Lardntr's Ninth Lecture.

cation were IOl .-t Llu1t4s VI
the machinery TO be en- ployed on board the steam
friga,es Missouri and Mississippi now: building.
and their preparation was matter gilmore difficult
" than had been anticipated A, some future time
they will be represented, ana in the meanwhile, l
ask your attention to few remarks upon the gen
eral topic.
The subject of river navigation, so Tar as con-
parison OF what mas been done in England and the
United States can DC made, is OF considerable mo-
ment. Tie question Of navigating rivers By steam
vessels in England Is different from what 1t j, here,
and one striking point Of difference j. found in the
superior .wifjness OF your boats Indeed. England
has none Of those streams which afford chan
mel FOR Navigation in this county
The Thames, one Of the Ionye.t lires OF steam
river navigation in that country, partakss more OF
the character OF the than OF river. and in the
portion near lis mouth to great exientis this
true that the boats YOU upon the Hudson
would be scarcely admissible there. The upper
portion Of the river, indeed. would admit .wiit
boats to be navigatcd Oh Its surface; but tho
roughly engrafted upon the miEds OK the pcop!e
sre the habits and the preiudces in favor o; sea
team navigation, that river boats are almost an
known. In form and general chsractec the boats
used upon the Thames and upon the CLYDE, which
for a lon- tine ha. been navigetcd by steam.
closely resemble ihese of sea-eong vessels. such
boats as we see upor the North and East Rivers
are quite unknown there. The English 81 not
make use OF long cylinders. OF thc expansive
power OF steam; in thee respects and in other
principles of con-idcr..Dc importance. the EnsIs.,
boats differ widely from those Of the ni,ed States.
Some years agu the question d swift river nayi-
cation was raised iN England and attracted tie
general attention OF Engineers and practical leH.
Canal uay- CATION then used sole!; Tor the trans
poria:icn ot merchandize-ite boats being drawn
81 horse, the OF sorse three or four miles
an hour NJ attempt was rsade upon canal BE-
tween Edinburgh AID Glasgow - transpo.. pa
sengers in boats drawn like the oilers by horses,
nut at much greater speed than wa, ever known
before The results OF this experiment gave rise
10 the discovery and development OF principle
new 10 sce1uic men, and Of vast importance II
river navigation. both in its theory and practice.
ai'urding one Of Many instances Of how important
Pari accident often plays IN the deyelopenent OF
truth.
The principle that governs the resistance OF bodies
moving through the water had long been known
and classcd among the settled laws of physics
prior to the time of Newton. The principle IS
this if 4 body pass through the wafer it suffers
certain resistance, owing 20 the displacement OF
jne illd, which increases with the speed Of tho
body Other things being equal, doubling the We
loci,y will produce four-fold resistance tripe
velocity will give ninetoid resistance qua
drIpc velocity increase the resistance TO sixteen
&c. This principle is mathemalically expressed
by the rule that the resistance of body moying
through fluid increases as the square Of the yelo
city.
This principle was received by all natural phio-
.o2hc:s without doubt for 1t long while, until the
period to which allude a course OF experiments
was then commenced upon this subject by Young
philosopher named Russell. He observed that
some boats upon the canal to which have made
alIusion, ran with speed which upon the priaci-
pies Just lard down wculd seem 10 be impractieabe.
After attaining, for instance, velocity OF seven
miles an hour the resistance accordlNg to tins pm
ciple would be fortyninc times great rs when thu
boat was going oae mile hour; til. would seem
to render its progress quite impossible. From this
circumstance. Russell was led TO suspect tallacy
in the rule laid down, since he could not believe
tina, the resistance increased in that enormous pro-
portion. He thereapon instituted series of tx
periments in some of which | was myself joined
with him and can therefore speak with ce1tainty
concerning them. We put swift horses to a small
iron skiii and found that so long the boat went
forward at the rate OF five miles hour the horTes
evidently worked with great difficulty and labor
But when their speed reached ten, twelve and even
fourteen miles an hour. the Gully difficulty with the
horses was 10 keep up their speed; in great
measure they were relieved from the labor OF
drawing the boat. We we're Immediately con-
WINGED that this fact which quite con-
trary TO the theory of Newton that the resistance
was in proportion to the square Of the velocity.
In searching for the causes of this phenomenon
our first suspicion that upon reaching certain
speed the boat GU, of the water; the draueht
was less at high than low rate, and tina, the re-
,i,tancc was therefore less. Although the general
rule held good until the boats speed reached
about seven miles hour, when II went beyond
that it iniled More resistance was destroyed by The
elevation OF the boat out OF water than aCqvlr9d
by the increased velocity. This tested by plac-
ing in hole in the bottom of the beat pcrpcndic-
uar glass tube, in which, by the common princi-
pies of hydrosatcs, the water would rise TO l eyc!
with that outside the boat. Tins OF course would
measure the draught Of water. We found thai;
when the speed rose beyond seven miles hour
he gauge fell, the water iz the tube sank until the
column was very small, thus showing the draught
of water was very light This will account Tor the
wondrous speed attained BY some Of your river
boats; the engine has power sufficient TO give the
BOAT speed enough 10 render the resistance very
slight.
But this elevation Of the boat is not the only nor
perhaps the principal cause OF the diminished re-
-isiance. Another effect mas been since observed
by Russell. When boat moves through suli
water, a wave is raised al the bow, which spreads
gu; obliquely To the two adjacent shores. This
wave OF body OF water increases in altitude until
a certain speed Is attained. when the beat passes
over and leaves it behind 1t that there j,
certain speed which this wave Is capable of al
tanning, but beyond which it cannot go. When
this Is reached there s. no head of water in frost
to obstruct the motioa of the boat and here ve
sec another OF the fact discovered by Russell
The practical effect o. this discovery was the e.
Adjustment OF boats for passengers which wen. at
the rate OF about ten miles hour on several OF