Natural History. 401 



ascertain if such were the case, I precipitated, by potash, the 

 oxide from a quantity of acetate ; the precipitate, when washed, 

 was dried by a heat of 220° until it ceased to lose weight : 100 

 grains, heated to redness in a tube, gave off nearly 8 grains of 

 water, and assumed the orange colour of litharge ; the recently- 

 precipitated oxide was no doubt, therefore, an hydrate ; part of 

 which, with somewhat less than two parts of olive oil, without 

 any addition of water, at a temperature of 212, formed, in half an 

 hour, perfect plaster. Each of these experiments has been re- 

 peated with precisely the same results. I am induced to mention 

 this fact, because all pharmaceutical writers limit the action of 

 the water to that of keeping down the temperature. H. H. 



III. Natural History. 



1. On the Insalubrity of the Air of Marshes in communication 

 with the Sea. By M. Gaetano Giorgini. — The observation of 

 M. Giorgini has been drawn to the state of the atmosphere in the 

 neighbourhood of certain marshes on the borders of the Medi- 

 terranean ; and by reference to historical data, and various docu- 

 ments, he has proved the great importance which attaches to the 

 circumstance of their being, at times, in communication with 

 the sea, so as to have a mixture formed between their waters 

 and that of the sea. Both ancient and modern authors have 

 announced the fatal effects produced in the neighbourhood of 

 marshes by such mixture, and a local belief of the same thing is 

 very common and strong ; the opinion has, however, never been 

 supported by any well ascertained and public fact, until the pre- 

 sent paper, which contains a case so much in point, and so in- 

 teresting, as to induce us to insert it at some length. 



On the south of the Ligurian Apennines, is a marshy shore, 

 bounded on the west for twelve miles by the Mediterranean, on 

 the south by the River Serchio, and on the north by the River 

 Frigido, a torrent commencing at the foot of the Apennines, in 

 the state of Massa di Carrare, running three or four miles over 

 the land, and then falling into the sea. The plain is from two to 

 four miles wide, and is traversed by a few short torrents or 

 streams ; among these are the rivers Camajore and Pietra-Santa, 

 which divide the plain into three separate basins. 



The rain and spring- waters, which flow into the three basins 

 mentioned, are slowly discharged into the sea by natural or arti- 

 ficial canals, penetrating the sand-bank, which exists on the sea 

 side ; these are, first, for the principal basin of the Lake of Mas- 

 saciuccoli, the ditch of Burlamacca; second, for the smaller Lakes 

 of Torre and Montrone, the ditches of Montrone and Tonfalo ; 



