Mr. Cuthbertfon’s Apparatus, Ge. 317 
natural hiftory; though inferior in fome refpects to many 
much fmaller but regular pearls, fuch as that in the pofleffion 
of the Jate Emprefs of Ruffia, which was worn by Charles XII. 
in his hat, and afterwards given to his fifter as a prefent on 
her marriage, and which is accompanied with two other pearls 
not much {maller; and the celebrated pearl of the King of 
Spain, called La Peregrina *, purchafed by Philip H. Fok a 
traveller, which weighs 25 carats; is valued at 150,000 
dollars, and, in all 7 aloe is the fir in the world. 
The above pearly excrefcence feemed to have been attached 
by the fimall end to a hole in the mother fhell. On the 
reft of the furface there was not the leaft appearance of art 
having beer ufed to give it its fingular form. 
XVII. Defcription of the Apparatus invented by Mr. JouN 
CurHBertson for producing Water by the Combuftion 
of Hydrogen Gas in Oxygen Gas. 
A BCD (Fig. 1, Plate VIII.) reprefents the inftrument 
and the veflel abcd in which it ftlands. The glafs bottle 
AD, which can contain about 1000 cubic inches of water, 
has a brafs cap which ferews off at A, and is perforated at 
the bottom, in which the picce ¢ f (fig, 2.) is ferewed. B 
and C, two glafs receivers, with proper mountings, the tops 
of which pafsthrough EF, a ftraight bar of brafs, are 
made faft to the bar by female ferews put on thefe tops, 
which are perforated perpendicularly, and have alfo a fide- 
hole correfponding with a hole in the brafs bar and with 
two holes in e f communicating with the large bottle. 
m and 2 are two ftop-cocks in the brafs bar, to fhut or 
open the communication between the receivers and the 
bottle. FR and E.N are two flat pieces of brafs made 
faft to the veflel containing the receivers, and which is 
* It was a produdtion of the pearl- fithery, near the gers ifland Mar- 
gatita, op the coaft of Comana,. 
nearly 
