Royal Society. 485 
this ingemous contrivance, do make now about 5 or 400 pounds 
a year by it^ All iummer long Ibme labourcrrs dig up and down 
in feveral places of the lame area, as in a kitclien garden j by 
which means they give way to the copious fulphureous fleams 
that are within the bowels of this mountain 5 and out of the fu- 
perficies of this earth, by means of earthen pots, they fublime 
the brimftone ; At the mouth of the largeft Spiracuky where 
there is an exceiTive heat, together with a conftant noife and 
fmoke, is found a fort of native lal-armoniac 5 itfeemsthe fteams 
arife in a liquid form; for if you put in a key, Iword, or any 
thing Iblid, thelc Effluvia will flick immediately to it and drf)p 
off like water: All this mountain mufl be very full of mineral 
fubflances^ for when the Effluvia are lublimed to the top of the 
Spiracula^ they are fecn flicking there to tiles or Hones, where 
they form this lalt, of which they gather yearly about 200 pound 
weighty it has much of the talte of the faflitious fal-armoniac; 
and, as an ingenious phyfician told Dr. Sylvefler^ beina diftiljed 
inafand furnace, it yields a volatile urinous fpirit, altogether like 
fal-armoniac, both as to its lenfible qualities and all other efJefls- 
the Dr. only oblerved that the Ipirit had Ibmething alluminoas 
in it, to correa which, they add a greater quantity ofquick-lime 
or fait of tartar, than in the diflillation of the common Ipirit. 
The Catacombs at Rome ; by Mr. James Monro. Phil. Tranf^ 
N*' 2(^4- p. (^43. 
TH E catacombs at Rome are a narrow gallery dua and car- 
ried a great way under ground, with a vafl many others 
going off from it on all hands, and alfo a vafl many little rooms 
going off from the principal and the fecund^ry ones too ^ thofe 
of San Sebafliano^ San Lorenzo and Sant Agnefe^ and thole in 
the fields a little off from Sant Agnefe are commonly fhevvn 
flrangers; they take their names from the churches in their neiah- 
bourhood, and feem to divide the circumference of the city with- 
out the walls between them, extending their galleries every where 
under it, and a vaft way from it, ^o that all the ground under it 
and for leveral miles about it, is laid to be hollow : Mr. Monro 
faw the catacombs at Naples^ and they fay there are catacombs in 
the neighbourhood of all the great towns of that part of Italy • 
fome authors will have them made by the primitive Ghriftians * 
adding, that in the times of perfecution they lived, held their 
affemblies, and laid up the bodies of their martyrs and confef- 
fors therein 5 this is the account that prevails at Rorae^ and in 
confequence of it men are kept conftantly at work therein 5 as 
fbon 
