70 PHILOSOPHICAL TRANSACTIONS. [aNNO 1776. 



under a necessity of going to Mahon in the evening; would you expect to be 

 serenaded on this rock with the croaking of frogs all the way you went? This 

 is literally the case. The gardens on each side the road are so much watered, 

 that the frogs, bred in the cisterns which contain the water, spread and enioy 

 themselves around, and frequently take up their abode in trees. This shows that 

 even the trees abound much in watery juices, as the exhalations arising from 

 them yield an atmosphere agreeable to the frogs. Where land is thus abundantly 

 watered and closely ];lanted with succulent vegetables, many parts of these veget- 

 ables, as well as the inse(-ts which feed on them, will be liable to ])utrify; and a 

 putrid vapour may be thence exhaled in the evening especially, and during the 

 night, when there seldom is wind to carry them off. Wherever the inhabitants 

 can find a proper depth of mould, within a convenient distance of a market, so 

 many sources of putrid exhalations are formed. 



Tlie 2d general cause of tertians was pointed out by Dr. Munro, physician of 

 this island, an ingenious gentleman, and very observant of every thing relating 

 to his profession. Tiie rocks of this island consist chiefly of 1 kinds of stone; 

 one so hard that scarcely any tool can touch it; and the other so soft, that it is 

 easily cut into any form. It much resembles the Bath stone, and is called Can- 

 toon stone. The first is impervious to any fluid; but the other sucks up or is 

 penetrated by moisture, like filtering stones. When houses are built on the hard 

 rock, all within the walls is levelled; and on that floor the poorer inhabitants 

 live. As this stone takes a greater degree of cold than substances less solid, and 

 does not so soon come to the temperature of the air; it consequently cools, and 

 attracts to it the moisture in the air, and retains it long on its surface. In order 

 to avoid the damj) cold feel, if the inhabitants can afford to buy a mat, thev cover 

 the floor with it; under which the wet remaining, induces a degree of putrefac- 

 tion, which renders the houses more unhealthy, and reduces the inhabitants to 

 a state ready to be affected by any distemper, especially by the tertian, which 

 spreads by contagion. As the moisture remaining on this stone is but temporary, 

 provided there are drains to carry the water oft", its bad eftectsare easily prevented 

 by keeping a fire burning, or by laying the ground floor with terrace, or with 

 deal boards. " ' ' . . . 



When houses are built on the soft Cantoon stone, the rain that falls without 

 soaks through it; and if there arc no means of carrying it oft"^ it remains in the 

 stone, becomes putrid, gradually exhales, and thus becomes highly prejudicial to 

 health. Several instances might be given of families dying in consequence of 

 such putrid moisture; but one may suffice, which became an object of general 

 observation. At a little distance northward of the line-wall, a loftv building was 

 erected for a house of entertainment. The people who inhabited it became very 

 unhealthy; and in a few years so much so, that 2 or 3 whole families died in it. 



