VOL. L.] PHILOSOPHICAL TRANSACTIONS. 7l 



the warmth of the waters, occasions a most plentiful perspiration. This is re- 

 peated for 7 or 8 days, increasing daily 2 or 3 cups of the water, till they come 

 to drink 25 or 30 cups a day. The operation continues from 8 o'clock in the 

 morning till noon. Some bleed once in the middle of the course, others not at 

 all. After they have finished this course of drinking, they bathe 2 days suc- 

 cessively, continuing in the bath -i- an hour, or longer, as their strength permits 

 them, or their case requires. This is the whole course ; which is repeated 2 or 

 3 times, or oftener, as they find necessary. The whole is concluded with a 

 gentle purge, though the waters themselves are of a laxative nature. 



There is another spring in the town of the same nature, but not so warm, as 

 the Prudel : it is called the mill-spring, and is only tepid. Those of a warm or 

 weak constitution make use of this instead of the other, both for drinking and 

 bathing. 



There are likewise several chalybeate springs in the neighbourhood of Carlsbad ; 

 one at 4- a mile, and the other at 2 leagues distance from the town. Both of 

 them seem to resemble the water of the Pohun spring at Spa ; but are not near 

 so strong. They are not used medicinally on the spot ; but are brought to 

 Carlsbad, and sold, in order to be drank with their wine. 



t^. An Essay tozvards Ascertaining the Specific Gravity of Living Men. By 

 Mr. John Robertson, F. R. S. p. 30. . 



To make some experiments on this subject, Mr. R. got a cistern made, of 

 78 inches in length, 30 inches wide, and 30 inches deep; for men of different 

 sizes to be immersed in. He then endeavoured to find 10 persons, such as he 

 proposed to make the experiments with ; namely, 2 of 6 feet high, 2 of 5 feet 

 10 inches, 2 of 5 feet 8 inches, 2 of 5 feet 6 inches, and 2 of 5 feet 4 inches. 

 One of each height he proposed should be a fat man, and the other a lean one ; 

 but he could not succeed in procuring such men ; and, after waiting till near 

 the middle of October, was obliged to put up with such as would submit 

 themselves to the experiment at that season of the year. They were all labour- 

 ing men, belonging to the ordinary of Portsmouth yard, and, except one or 

 two of them, who were middling sized men, were for the most part very thin 

 and slim made persons. A ruler, graduated to inches, and decimal parts of an 

 inch, was fixed to one end of the cistern, and the height of the water noted 

 before a man went in, and to what height it rose when he ducked himself 

 under its surface j and of these several observations is the following table com- 

 posed. 



