«54 Utililj of emplqyiitg Culcarcous Suhjlancss 



peiTe(5lIy confiftent with the principle I have for fomc time 

 •been led to receive as true, that I wifla for its exienfive 

 circulation. 



Yours with eftccm and regard, 

 Mr.TiLLOcH. SAM. L, MITCHILL. 



Cbpj cf a Letter from Hippoljto I. Da Cojia, Efq. Brafilian. 



" DEAR SIR, Nfiv-York, Ma)'21, 1799. 



•' YOUR theory, in regard to the a6tion oi alkalis and cal- 

 tareous earth upon fepton, or the principle of corruption, is 

 fo well proved in the feveral papers you have publiflied, that 

 it is needlefs to adduce further proofs to pcrfons of know- 

 ledge: but as additional fafts may be ufcful to perfuade 

 people of lefs information or more prejudices, I believe I 

 agree with your wiflies in prcfenting to you an account of 

 the influence of calcareous earth upon the putrid effluvia in 

 the city of Lifbon^ which is^ I think, a proof of the moib 

 interefting nature. 



" The city of Lifbon is fituatcd on the northern bank of 

 the river Tagus, about eighteen milts from its mouth : it is 

 about fix miles in length, and its breadth is in fome parts 

 two, in fome three miles, although in other parts veiy nar- 

 row. In the moft inhabited part of the city there are fcven 

 hills or mountains, which, of courfe, occafion declivities and 

 lower filuations. This city may be divided into the neiu 

 and old city ; becaufe there is a fpot which was overthrown 

 by the horrible earthquake of the year 1755, and was re- 

 built : I call, therefore, this part the new citv. The ftrectj 

 in this quarter are very regular, the buildings neat, and the 

 pavements for foot paflfengers very commcjdious ; but the 

 fituation is almoft all very Iq-ia-, 



" The old city, or the part which did not ftifTer fo much in 

 the earth(]uakc, and preferves its ancient buildings, is in the 

 Gothic tallc, with narrow and crooked ftreets, in the moft of 

 which there are no pavements for foot paflcngers; the houfc.s 

 arc fo high, that, in fome of the narrowed ftreets, the fun 



cannot 



