The enquirer. [volume] (Richmond, Va.) 1804-1815, 1811-01-12

theory vulnerable In many points. I hav.
sid that the swiftest motion had place a
midnight. that The cycloidal notion of the
Earth could give but one tide in twenty fouI
hours; that the true cyclotliai curve wa
| described only Mt the solstices that at the
| equinnSes when some writer's think we
ought to have the greatest tides, the effec
from this cause will he nothing or very
small and have admitted the possibility
that this motion might BE- found to cause
some OF the very many Irregularities to which
the tides are subject. and particularly of tho
western current which prevails in the ocean
bat as an Hypothesis nn'y, without investira 4
ii M. AS this question has caused much con:
versation on the tides, and rs the manner o
accounting for them, from the principles Of
gravity, is not famili,r,y known: I have
thought itmight not he unacceptable to give
a slight koch OF the p inciDlcs. It wouid
be impossible in publication Of this kind
to give any hing ike an adequate idea of
| the h DRY as treated of BY modern mathe ~ "a,
ticiaas bu. some information may be deri-
we'd from what follows. >.
IN he elements ct mechanical philosophy,
by the late professor Robson of Edinburg,
we lind abou, one hundred pages on this sub
Ject, from which 1 have selected such pas
stges as serve to convey most easily some
4
5Sl.) BY comparing the actual quantity
OF matter in the earth with that in the. sun,
he tiads the suns force 10 raise the tides TO
be 24A inches. (page 5e7) The distance of
| the sun being 800 times that uf the Moon.
and the quantity of matter in the sun being
33S000 tunes that of he earth (found BY a
rule the truth of which is incontrovertible. J
| 1T The quantity OF matter in the moon, wer,.
| equal TO thar in the earth, her accumulatinr
force would be 17S times greater than that
OF the sun !; 1t is really 81 times greater Ito
be proved hereafter) whence we infer that
the real quantity of matter in the moon is
the quolient of these, that is about IL part
OF mat in the earth. In page 603) He SAYS,
did we know the real quantity of matter
IN the moon, the force of the moon tn that
o, the earth, would be determined i'm a nil
mute. and the mutation of the earth's AK
is, is the only observation that can rive ns
real Information on this subject, but he thinks
he nu alton and procession too small TO give
very exact idea of the proportions and
Therefore he prefers the obscrva inns made
| ut Brest and Rochtort on the tides during six
years OF which he SAYS twas not till this
noble collection of observati ons that the phi
| losopher could assoit and combine he i'm
inense variety of heights and times of the
udes so as Ia throw them into classes, and
| u compare them with the Newtonian the
! DRY (page 6O4) He gives four different me =
| tnods, to determine the relative forces of
the sun and moon in all which the antece
| dent OF the several ratios IS 5 and the Goa
sequents 2 is I-30, 1-l2 9 Ia the
| mean being 2. IS dec and then adds-'thus
! II appears ihat all these methods give near
| y tine same result, and tina, we may adopt
to 2, as the ratio of the disturbing tor
ces his agrees ex remedy wei! with the
n mo ra,to u
on; now the suns effect being 245 inch
es, Thar of the moon must be SIS inches.
VIZ. 2 IS y "a l-2 the sum is 80 9 in
GEES Tor spring tides and the diff, renee
So IL or neap-tide, AT a mean (page 662.l
we nave several series of phenomena
which tally we'll with the theory. tia
the real source of them can 10 longer be
doubted and tho Delaplace proceeds in
a different way, yet his main interences per
ieciiy agree with those already Diet rmined.
nave gwen these quotations rom Robi-
sons works IN preference to any other. be
cause u is written in simple, vet tr. Iy
scien'l1c style. by a philosopher OF great
iio'tity, and published so late as 1904. Tie
only objection which can be T ade e. this.
| Is thai he mass of the M IS dete min ii
| nom the tides, but his oDiccti n is ooyiated
! by Delaplace who has found the mass of %
Moon independent OF The tdes from celes-
tai phenomena three different ways to be.
h 50. 2, So, 6 and "A. 3 part of the Earth.
lie says IN canique celeste. second par.
book 6, page 1907
! La vaieur la plus vraisemblable de la
masse de la lune que me parait resulter des
divers phenomt mes est 1-685 de celle de
la terre. Lerapport de Faction dc la lune
eeile Gu sclei sur la mer est alors eeal
1850 dec or 2 l-2 times that of the sun, til,
same as that given by Roblsoa and by
| Newton.
The sum is, that the masses of the Sun.
Moon and Earth, are known, as deduced
from the principles of gravity, independent
OF tine experiments made at Brest and Roch
iort on the tides; from which the forces
that the two iuminaries ought to exert to
raise the waters is known, and the expe-
riments ar found to agree with thu. Theo
! ry. have merely given these extracts that
the public may see what data they have To
determine tins question.
| L will thank the Editor of the ENQUIRER IN
! publish the above, as it will remove an i'm
preston which the public may have receiv-
ed, relative to my apparently partial re-
! port OF cases. Some may think these topice
Obtrusive or imperiinent in a newspaner
yet there are many 70 whom they are inter
est,ng. There is moral Ger ainty that fine
merit of every question, depending upon
| mathematical principles, must be ultimate
y manifest, II is therefore important that
such should be fully discussed.
GEO. BLACKBURN,
w. q NJ COL
| Williamsburg ian. 10 1910.
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