Burlington free press. [volume] (Burlington, Vt.) 1827-1865, 1847-01-08
COMMUNICATION

To the Editor of the Free Press.
SiR-As the public mind is now much occupied with
Railroads, it would think, be gratifying to many Of
your readers if You OF your scientific subscri-
5'rs would give through your valuable paper
plain and practical information relative to the friction
or resistance to bodies moving a level track and
the propofilonatc increase OF force required
the weight over an ascending grade from level to
sixty feet and also why short but severe grades on
what are called unduaiing roads, tolerated, while
a long grade but no hghers objected to- Or, in other
words, ia given quantity with a given power can be
moved l. miles per hour grade Of 60 feet tho
mile tor one mile, why not for and twenty miles!
N.
We should be glad if We were able to give
the interesting and valuable information suggest
ed by our correspondent lie is probably well
aware, however that the subject Of the raiue At
gradients on a giren line Of railway has been ex-
aminad with some thoroughness by scientific En-
gnccrS, and that the solution of the problem has
been arrived al by means Of algebrac formulas
and equations. Mr.. CHARLES ELLEr. distin-
gushed Civil Engineer in Philadelphia, in Sc
ries Of very able papers communicated to the
journal otthe Franklin Institute some tim, since,
examined at length and with great clearness and
force, the question of the cost of transportation
on railroads" which, Of course involves a con-
sideraton of the raiuc Of gradients, as well as Of
the value of time, the amount and character Of
the business 10 be done &c. &c. Oar corrcspon-
dent, and any Of our readers who feel an interest
in the matter, can probably find the Journal Of
the Franklin Institute in the Mechanics Library,
and in the volumes COR 1913, and 4, they will
find the papers alludedto.
! We suppose it is undeniable that no il,,ariqbl,
value can be assigned to grades-that is. that
no formula can be adopted which shall be Of
universal application to all railroads, and thus
enable us to resolve, by equation, the abstract
value OF gradients. The data which must enter
into and govern the solution Of the problem re-
cessary vary with the circumstances Of each
particular road Our correspondent will hardly
wish to be understood, we presume, that "tric.
tion' or the increase 9ff5rce' required to over.
come an increase ot"triction,' is the only cues
lion to be determined in estimating the impor.
lance of high or low grades. \ grade th,t might
| be almost unoblccuonable on one road. mirbt be
in the highest degree Objectionable on another
50 inconslderable the influence Of friction alan.
in determining the question.
Mr.. ELLET, in the examination to which W.,
| have referred arrives at certain conclusions tb,,
are well calculated to surprise those who are in.
experienced, or Ignorant. in railroad matters.
T among whom we include ourselves For exam.
PIE: lie assumes road Of so miles length-n
limit grade of 40 feet-freight 10000 tons. Of
which 10000 tons is to ascenithe grade.-eros.
weight Of cars, freight, and passengers O.OOo
tous,-number Of through passengers 10000
and the power OF the engines equal to the COM
mlnd of 800 tons gross on level. On these d.
IA he shows, by inserting the values provided bv
the data in equation, LIST That, in order to reduce
, tie maximum or limit gradient ten feet, it would
bradysable TO eXpend but $50 600 %. Tbo, !,
order 10 reduce the length of this road one p,ls i,
would be advisable TO expend $4,000; Sd Tbo,
on such road, the rdlae Of ten feet in The ero1
is onlyeqaal to FOUR SEVENTIES Of mile in a6,.
ta"re Of 80 aiics-'a fact" as he pointedly OBJ.
serves, THAT should prompt us to be on our guard
"when we attempt to reduce the grades of a road
= "by an increase of distance, before we have ex.
"amIned we'll into the character and amount of
"the trade to be accommodated"
e We suppose, also that the relative value o,
: "nndnlaiing roads" and roads of long grade
u Of similaraccliyity, to be determined by va
+ reiy of circumstances, The grades might be SC
# disposed on the latter line, for instance, that aux
It Hilary power could be so employed as to rende
Il the expense oitransportation less than on the nm
dulating road, other things being equal. Gu
= correspondent will readily see this
p But we have said more than we intended 10