( * 97 ) 
Aliquando enim tarde & cum peflimorum Symp- 
tomatum Satellitio erupere variolas; aliquando in- 
caflum ceflit Incifio ; ilia tamen loca Inoculationis 
ulceribus cacoecheis repleta fuerunr. Nonnullis etiam 
lsthalis fuit ralis Operatio : Mumia enim fermen- 
tativa, e marcidis iftis tuberculis, rancida ac veluti 
cadaverizata non folum expetito fcopo haud fatisfa- 
cit, fed pravam fanguini poteft communicare putri- 
laginem. * 
VII. An Abflraft of a Letter from Petrus Van 
Mufchenbroek, M D. F. S. Trofeffor 
of Mdtbematicks and Aftronomy in the Univerjity 
of Utrecht, in Holland ; to Dr. J. T. Defa- 
guliers, F. S', concerning Experiments made 
on the Indian Magnetick-Sand. 
SI R, 
I Don’t know whether I dare take up your Time 
with my Trifles ; yet I’ll venture for once to ac- 
quaint you with fome things concerning the Indian - 
Sand, which is attrafted by the Load (bone. 
The Indian-Sand which is brought to Holland , 
is Laid to be chiefly gather’d upon the Sea-lhore in 
Perjia ; then it is boiled in Water, to free it from 
its Saltnefs, and it is after this a black Powder, con- 
fining of Grains of different Bignefs ; fome of which 
have a very rough Surface, and others have one part 
of their Surface fomething rough, and the other very 
fhining: Their Figure is very irregular, like Grains of 
com- 
