2. In the construction of cities, narrow streets and alleys should be carefully avoided. Deep lots should be reserved for yards and gardens for all the houses, and subterraneous passages should be dug to convey, when practicable, to running water, the contents of privies, and the foul water of kitchens. In cities that are wholly supplied with fresh water by pipes from neighbouring springs or rivers, all the evils from privies might be prevented by digging them so deep as to connect them with water. Great advantages, it has been suggested, would arise in the construction of cities, from leaving open squares, equal in number and size to those which are covered with houses. The light and dark squares of a chequer-board might serve as models for the execution of such a plan. The city of London, which had been afflicted nearly every year for above half a century by the plague, has never been visited by it since the year 1666. In that memorable year, while the inhabitants were venting their execrations upon a harmless bale of silks imported from Holland, as the vehicle of the seeds of their late mortal epidemic, Heaven kindly pointed out, and removed its cause, by permitting a fire to destroy whole streets and lanes of small wooden buildings, which had been the reservoirs of filth for centuries, and thereby the sources of all the plagues of that city[22]. Those streets and lanes were to London, what Water-street and Farmer's-row are to Philadelphia, Fell's-point to Baltimore, the slips and docks to New-York, and Water-street to the town of Norfolk. [22] A proposal was made to replace the houses that had been burnt, by similar buildings, and upon the same space of ground. Sir Christopher Wren opposed it, and with the following argument: "By so doing, you will show you have not _deserved_ the late fire!" 3. Where the different forms of summer and autumnal disease arise from marsh exhalations, they should be destroyed by drains, by wells communicating with their subterraneous springs, or by cultivating upon them certain grasses, which form a kind of mat over the soil, and, when none of these modes of destroying them is practicable, by overflowing them with water. I have met with many excellent quotations from a work upon this part of our subject, by Tozzetti, an Italian physician, from which, I have no doubt, much useful information might be obtained. The Rev. Thomas Hall, to whom I made an unsuccessful application for this work, speaks of it, in his answer to my letter, in the following terms. "It is in such high estimation, that the late emperor Leopold, when grand duke of Tuscany, caused it to be re-printed at his own expence, and presented it to his friends. The consequence of this was, it influenced the owners of low marshy grounds, in the neighbourhood of the river Arno, to drain and cultivate them, and thereby rendered the abode of noxious air, and malignant fevers, a terrestrial paradise."