VOL. XXXVIIl.] PHILOSOPHICAL TRANSACTIONS. 047 



the places where the incisions had been made. Moreover in some instances 

 this mode of inoculation terminated fatally. 



Experiments on the Indian Magnetic Sand. By Dr. Muschenhroek. 

 N° 432. p. 297. 



The Indian sand, which is brought to Holland, is said to be chiefly gathered 

 on the sea-shore in Persia; after which it is boiled in water, to free it of its 

 saltness; after which it becomes a black, powder, consisting of grains of dif- 

 ferent sizes; some of which have a very rough surface, and others one part of 

 their surface something rough, and the other very shining. Their figure is 

 very irregular, like grains of common sand; only this Indian sand is smaller. 

 These little lumps have neither taste nor smell, and are friable, so as to be 

 easily reduced to a very subtile powder. It has some parts, which are strongly 

 attracted by the loadstone; and others so very inactive, as scarcely to seem to 

 be magnetical at all; the blackest are the strongest, but the inactive ones are 

 more shining, and inclining to the colour of lead; these are in the greatest 

 quantity : and from them the others are got out by a loadstone. Montenus 

 has several ways examined such a kind of sand, which is brought from Virginia, 

 and described it in Phil. Trans. N° 197. Dr. Muschenhroek examined the In- 

 dian sand another way ; of which he gave an account in his Physical Disserta- 

 tions, p. 127. But a great deal still remained to be considered; and as there 

 is much more of this substance of the inactive than of the active or magnetic 

 sort, it was proper to try, wliether a magnetic virtue might not be excited or 

 increased in all of it; and after a few trials he found the thing succeed. He 

 suspected that there might perhaps be too great a quantity of sulphur ad- 

 hering to the sand, to suffer it to be turned into any metalline regulus by a long 

 continuance in the fire; he therefore toasted it in an open crucible for 2 hours, 

 with half the quantity of pot-ash; he afterwards washed away the salt with 

 water, and the sand remained much blacker than before, of which he found 

 more than a quarter endued with a greater magnetic force. Muschenhroek 

 does not scruple to attribute this virtue to the salt; because, though the action 

 of the fire alone does increase the force of the sand, yet it does not give it 

 near so much attractive force. 



And because common black soap is made of oil boiled with a lixivium of pot- 

 ash, he had a mind to try whether soap might not do more than salt alone in 

 exciting the virtue in the sand ; so he mixed the sand with an equal quantity of 

 soap, which he first exposed to a gentle fire in an open crucible, to dry up the 

 soap, which swells very much: then the fire was heightened for \ of an hour. 



