174 Intelligence and Miscellanies. 



most correct and important." It is not possible to do jus- 

 tice to the statements of Mr. Walker without copying his let- 

 ters entire. The most important results however are that 

 cast iron pipes of any necessary diameter, even to two or 

 three feet, may be employed — that their strength is suffi- 

 cient to resist any desired pressure, when the thickness of 

 their sides is very trifling, three quarters of an inch being 

 sufficient for pipes of twenty inches diameter — three eights 

 of an inch for ten inches, and three sixteenths for a five inch 

 pipe ; that the pressure, with a head of one hundred and for- 

 ty feet, is about sixty-two pounds on the square inch, 

 " which is much less than one tenth of pressure which a good 

 easting of one foot diameter and a half inch thick, is capa- 

 ble of resisting: the tenacity of a square inch of the best 

 cast iron, having been found by experiment to exceed twen- 

 ty thousand pounds''* — that the joints of the pipes can be 

 rendered impervious and secure — that the iron is very en- 

 during — imparts no disagreeable taste to the water — is, when 

 properly prepared, always to be depended on, and in the 

 course of years is more economical than any other sub- 

 stance. 



The joint used in London, for connecting the pipes is the 

 spigot and fauset, made tight in some cases, by lead cast 

 around, and in others by a cement which is composed of two 

 pounds of sal ammoniac with one hundred pounds of borings 

 of iron, with the addition of a little sulphur. These mate- 

 rials are mixed with water which " oxidizes the iron, and 

 in a short time the mixture becomes extremely hard and 

 quite impervious to water." 



When lead is used it is contracted by cooling, and it is 

 necessary to upset the joint with a hammer and chisel. 



The following extract of a letter to the Editor, dated, 

 December 25, 1822, from Mr. Vaux, contains much valua- 

 ble information. 



" Our experience I consider to be decisive, especially in 

 relation to the all important matter of the joints of the con- 

 duits. 



* The proof of these pipes and cocks is made by the hydraulic press and 

 those sent out by Mr. Walker to Philadelphia, were proved by a pressure 

 equal to a column of water of three hundred feet in height, that is of the 

 weight of nine or ten atmospheres. 



