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Hollow Pyramids and Cubes , 
PLATE I. N° III. 
Figures of Spring-Salt. 
After the Defcriptions already given, his 
needlefs to fay more of the four following 
Figures, q , r, s , t, than that they alfo are 
hollow pyramidal tranfparent Bodies, with 
fuch different Graduations as themfelves 
pretty tolerably reprefent. 
v, w - Two of the large hollow Pyra¬ 
mids of Mr. Lowndes's Salt, drawn in fuch 
a perfpedive View as may heft exprefs 
their real Figure; each having a fquare 
Bafe, and four triangular Sides that are 
nearly equal. Many fine Lines appear run¬ 
ning acrofs thefe Sides parallel to the Safe, 
which* op a flridl InfpefBon, are found 
to be a regular Graduation of Steps, leiTen- 
ing from the Bottom upwards. Thefe Py¬ 
ramids do not commonly end in Points, but 
are terminated by a cubic Figure: each Cor¬ 
ner of their Bafe is alfo frequently fupport^ 
ed by a Cube, but of a fmaller Size - 3 and 
ftill Idler Figures of the fame Shape appear 
along the linear Edges, in Number equal to 
the Steps, and doling the Angles where 
they join. There are Graduations within- 
|ide thefe Pyramids correfpondent to thofe 
■without, like the Underwork of a Pair 
of Stairs. The Size here exhibited is 
but 
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