1S8 
On the Sandstones of the Quarries near Agra . 
£May 
Explanation of the Table • In the above table we have been compelled to sub- 
stitute some abbreviations, in order to bring it within the compass of the pa^e. C, 
means courses ; M. S. main sail; T. S. topsails; F. T. S. fore-topsail; M. T. S. 
main topsail ; T. G. S. top-gallant sails ; J. jib ; Sp. spanker; St. staysail ; F.J. 
foie jib ; Tr. trysail ; R. royals ; T. G. S. S., top-gallant studding sails, &c. 
In the heading of the columns “ Angle of heeling” means the inclination, as 
measiired from a longitudinal vertical plane. “Angle of pitching” signifies the in- 
clination, as measured from a transverse vertical plane. In the column “what 
tack, L. stands for larboard, and S. for starboard. 
Remarks by the Editor. We have added to our correspondent’s table, in the 
ast column, the apparent velocity of the wind, roughly derived from bis hypothetical 
estimate of its force and denomination. So far as it is to be trusted, the opinion 
advanced by Q. is fully borne out; for, with the wind on or before the beam, we 
bnd, throughout the table, ample evidence of the vessel’s attaining superior velo- 
citv. One of the most interesting consequences of this fact, now" so nearly esta- 
blished, is the exact correction which it will afford of the position of the” ship’s 
vane, and a knowledge of the best disposition of the sails. Thus, when the an<de 
of the wind appears in the table 67° 30' or 22° 30' before the beam, it is really 
as much or more abaft the beam, and the sails (having an angle of 30° with the 
fore and aft line by the table,) are really situated very nearly at right angles to the 
direction of the wmd, and therefore in the most advantageous position. But we 
will refrain from enlarging upon these fruitful subjects of speculation until we 
are favored with more perfect data ; and we need not assure W. R . N. that his 
meritorious labours shall always meet with a ready reception in the pages of our 
humble repository. 
VII. Observations on the Sandstones of the Quarries near Agra, and 
Results of Experiments made thereon ; by Lieutenant J. T. Boileau, 
of Engineers . 
. experiments recorded in the following communication were undertaken 
o?i c ?^ se R u e nce of an objection which was made to a suggestion of mine to 
su j statute slabs of sandstone, spanning from beam to beam in flat roofs, instead 
tuloi ber & a/ts \*P? roofing tiles as is in general practised. It was said that a 
stab 24 inches thick, as proposed by me, would not bear the weight of the peo- 
ple employed to beat down the terrace ; and further, that a roof upon the above 
principle would not probably be watertight. It will be seen, by a reference to the 
annexed tables, that the least weight which was capable of breaking one of 
and 7w’ WaS 304 lbs * : tbese were onl y H inches thick, 
a slab of 2^ inches would ( cceteris paribus ) require a weight of 844 lbs. to 
'*“1® a „ ct V re < n,ore , than ' under an y circumstances, it could be subjected to in 
1 “,*' Having completed many roofs upon the above principle, I can also sav 
over r/ifl e '? r ry . ,nstan , c ? Pr ove <J perfectly watertight ; and the terrace laid 
clacks tl,»n ■ \ aVC ‘Variably found to dry more uniformly, and freer from 
strurtinn , ' vben , brld f™i? J. olsts Have been used. Roofs of this con- 
tle af entt™ T ’ ec T m "r al ' and , , lastm ff. and, wlien once completed, require lit- 
•«“ aftcrwards ; tbe sn ’ a11 quantity of wood used in their construction 
X ‘ h ™ urc a S a, " st fire > and renders them safe from the attacks of 
eying sketch represents a sec- | 
tion across the gii’ders of a jr 
lootof this construction, where 
A. A. are the girders ; a. ,v. the 
slabs of sandstone, rabbeted 
together, and cemented with 
fine lime ; 1 . 1 . the terrace laid ~ 
on 4 inches thick, and beaten down to 2 inches. 
bricks aS^morta^dlstant^ ' d f U< f“ g ^ ex Periments, consisted of two pillars of 
iron. The sn 1 tu t clea ^ a scale ’ and * ™und bar of 
having a bearing on tbp wu ’ \ oug ’’ 12 * nc h es broad, and 1| inches thick, 
n^ove umvS g on ? f 3 in , ch ? s at each end. The ends were free to 
* lie application ot the weights, which were laid on at slight 
1 Bridging* joist. 
