238 Comvmnication from Dr. Miichilf. 



of the Lifbon buildings comes, and the foil is in a grca? 

 part calcaieous. Thele places are pointed out as the feat of 

 health, and, indeed, are the moft beautiful and pleafant 

 fummer retreats you can iniaoine. 



" After this rtatemcnt, can any body attribute thefalubrity 

 of Lifbon to its climate merely? Certainly not: becaufe L 

 obferve, that where there is calcareous earth there is no in- 

 fetSlion, notwithftanding the continual exiftence of putrid 

 exhalations ; and where there is not calcareous earth, and 

 the foil is fandy, gravelly, and clayey, there are fevers, al- 

 thouo-h the climate is the fame; the diltance of thefe places 

 being only the breadth of the river, about three miles. 



*'To thtfe unanfwerable fatSts I muft add, that I have ob- 

 ferved, two or three times, in Lifbon, dead animals upon 

 the ruins of houfes, and of courfe furrounded with calca- 

 reous earth, in a llate of deficcation ; and, at the fame time, 

 two or three fathoms diftant, another animal dead too, and 

 lyino- upon another kind of foil, in a ftate of complete pu- 

 trefaftion. The reafon of their prcfervation is obvious : the 

 fcptic acid was abforbed by the calcareous earth as foon as 

 it was formed by the union of fepton with oxygcnc ; like- 

 \\ife, the oil formed by the union of their hydrogcne with 

 carbone has been imbibed, the water formed by the junc- 

 tion with oxygene evaporated, and the remaining parts of 

 the animal were left in a dry Hate. 



" The eft'efts of calcareous earth and alkalis feem to be very 

 well underftood by the people of Portugal : they put chalk 

 and plafter with the bodies they bury in the churches j and 

 they wafti with plafter the rooms where there have been any 

 fick or contagious diforders. This precaution they never 

 ojxiit. — I pray you to accept my belt wifhes. 

 " I am, dear Sir, 

 " Your's, veiy fincerely and afl'eftionately, 

 " HIPPOLYTO L DA COSTA. 

 *' Samuel L. Mitchill, Efi." 



Ill, An 



