PYR 
PYR 
laining the sarcophagus, a narrow sane- that is wanting, and the solid content of the 
tuai y, which is the sole end and object of an frustrnm, or broken pyramid, will remain, 
edifice so stupendous, so collossal.” Every pyramid is equal to one third of its 
We have thus enabled the reader to com- circumscribing prism, or that has the same 
pare the two latest accounts of the pyramids 
of Egypt, and it will be found that though 
they differ in the method of description, 
that each author has been correct in stating 
the facts relating to them. Denon con- 
cludes his detail with several just and severe 
observations on the pride of those by whose 
oi;der they were erected, and the barbarous 
ignorance and stupidity which governed 
those who obeyed its dictates; and yet, 
strange as it may appear, it becomes neces- 
sary to mention a pyramid erected by the 
very Frenchmen who having visited Egypt, 
and witnessed the effects of ancient des- 
potism, perversely imitated the devotion of 
its inhabitants to a military idol, who has 
woefully convinced the world how little 
that devotion is deserved. 
Tlie pyramid alluded to is situated in 
Holland, was designed by the chief of the 
battalion of engineers of the French army 
there, is 110 French feet high, exclusive of 
an obelisk on the summit which is 42 feet 
more ; and the sides have four inscriptions, 
three adulatory, and the last to the follow- 
ing purport : “ This pyramid was raised to 
the august Emperor of the French, Napo- 
leon the First, by the troops encamped in 
the plain of Zeyst, being a part of the 
French and Batavian army, commanded by 
the Commander in Chief, Marmont.” As 
30,000 men assisted in this undertaking it 
was completed in 32 days, in the year 12, 
by their computation. 
Pyramid, in geometry, a solid, standing 
on a triangular, square, or polygonal bases, 
and terminating in a point at the top ; or 
according to Euclid, it is a solid figure, con- 
sisting of several triangles, whose bases are 
all in the same plane, and have one com- 
mon vertex. 
Hence the superficies of a. given pyramid 
is easily found by measuring these triangles 
separately ; for their sum added to the area 
of the base, is the surface of the pyramid 
required. It is no less easy to find the solid 
content of a given pyramid ; for the area of 
the base being found, let it be multiplied by 
the third part of the height of the pyramid, 
or the third part of the base by the height, 
and the product will give the solid content, 
as is demonstrated by Euclid, lib. 12. prop. 
7. If the solid content of a frustrum of a 
pyramid is required, first let the solid con- 
tent of the whole pyramid be found ; from 
which subtract the solid content of the part 
base and height ; that is, the solid content 
of the prism is equal to one-third of the 
prism. For supposing the base a square, 
then does the pyramid consist of an infinite 
number of such squares, whose sides, or 
roots, are continually increasing in arithme- 
tical progression, beginning at the vertex 
or point, its base being the greatest term, 
and its perpendicular height the number of 
all the terras : but the last term multiplied 
into the number of terms will be triple the 
sum of all the series, equal the solid content 
of the pyramid. 
All pyramids are in a ratio cbmpounded 
of their bases and altitudes ; so that if their 
bases be equal, they are in proportion to 
their altitudes ; and tnce versa. Equal py- 
ramids reciprocate their bases and altitudes ; 
that is, the altitude of one is to that of the 
other, as the base of the one is to that of 
the other. 
PYRITES. Iron, in combination with 
sulphur, forms a mineral substance, which 
has been long known under the name of 
Pyrites, and which is very extensively 
diffused. It occurs massive, disseminated, 
and frequently crystallized : the forms of 
its crystals are various, but the most com- 
mon is the cube regular, or modified by 
truncation of the angles or edges, or accu- 
mination of three planes on the angles : the 
octaedron, dodecaedron, and icosaedron, 
also sometimes occur. 
Its colour is brass-yellow, varying a little 
in the shade, and the lustre is always fully 
metallic : it is opaque. The fracture is 
uneven. It is brittle ; its hardness is such 
as to strike fire with steel ; its specific gra- 
vity is from 4.6 to 4.8. By friction it 
exhales a sulphureous smell. This odour is 
strong when it is heated before the blow- 
pipe; it gives at the same time a blue 
flame ; and at length a globule of a brown- 
ish colour. It is soluble in nitric acid, 
with the disengagement of red vapours. It 
is not sensibly magnetic. Various analyses 
of it have been given : according to those 
executed by Mr. Hatchet, it consists of 
Sulphur 52 
Iron 48 
100 
Besides this, which may be named com- 
mon Pyrites, there are some others which 
may be regarded as varieties of the species, 
