VOL. XV.] PHILOSOPHICAL TKANSACTIONS. 239 



oculutn, as plainly as water running in a river, and more rapidly than any 

 common stream." The same experiment I repeated again before them on the 

 2d of June following, and to those that had good observing eyes, the circula- 

 tion was as visible outwardly on the hands and toes, as in the vessels within. 

 But certainly the appearance in the vessels on the forementioned sacculi, with 

 the beating, emptying and filling of the heart, is most surprising to the be- 

 holder. This creature seems wonderfully adapted by nature for this experiment i 

 for besides the transparency of its skin and vessels, I have had them live Q hours 

 after they have been expanded, and all their viscera laid open. 



To Dr. Garden's 2d letter I have only this: he there endeavours to explain 

 the trade winds within the tropics, from the different gravity of the atmosphere 

 at divers times of the year. And yet it is asserted in N° 165 of thePhilos. 

 Trans, that the mercury is not affected with the weather, or very rarely, whether 

 it be cloudy, rainy, windy, or serene, in St. Helena, or the Barbadoes, and 

 therefore probably not within the tropics, unless in a violent storm or hurricane. 

 Now if the mercury move little or nothing in the baroscope, it is likely there 

 is little or no change in the gravity of the atmosphere within the tropics. 



On Dr. Papin's fVay of Raising Water, By Dr. Nath. Vincent, F. R. S. 



N° 177, p. 1238. 



I have inquired into Dr. Papin's problematic engine for raising water, in 

 N° 173, (p- 193 of this vol.), and conclude it may be solved after this manner. 

 Within his rock CC, (fig. 5, pi. 5,) there may be a vessel placed, which 

 shall be made like the body of a pair of bellows, or those puffs heretofore used 

 by barbers, which being filled with water, a piece of clock-work put under it 

 may produce the jets; the water being received into the shell HH, and running 

 thence into the hollow of the coral E E, may be thereby conveyed into the 

 follicular cavity, in the same quantity as it is ejected from the two emerging 

 tubes; and it shall circulate 100 or 1000 times, according to the going of the 

 clock-work. If some such account as this will unriddle the engine, the con- 

 trivance of it is owing to a theory communicated by myself, &c. 



On the same Subject. By Mr. R. A. N° 177, p. 1239. 

 I conceive that the air is forced into the outer glass at the bottom of M. 

 Papin's machine. That it then passes up between the two glasses. That the 

 outer glass or case being close luted at the head or crown, to which the inner 

 glass is hung by the coral, the air is forced into the mouth of the inner glass. 

 That the air, so fo/ced, pressing on the surface of the water that covers the 



