Decay of Oaspipes in certain Soils. 19 



Water boiled with the powdered material of the pipe 

 showed evidence of both sodium and chlorine abundantly 

 present in solution — in fact, it is to the presence of common 

 salt with concomitant agencies that the rapid transmutation 

 of the cast-iron main may be attributed. 



When the clay in which the pipe was imbedded is 

 examined two points become conspicuously apparent — 1st. 

 The clay, retentive of moisture, is also so harsh and porous as 

 to be permeable to air. In this sense it is the very opposite 

 of " fat," water-tight, and consequently air-excluding clays. 

 A block of this clay air-dried, when placed in water, rapidly 

 falls, crumbling away in a surprising manner, at the same 

 time releasing much air, and forming a gruel-like magma at 

 the bottom of the water. A pipe of cast iron laid in this clay 

 is, on account of the properties just mentioned, subject to the 

 continuous and joint action of moisture and atmospheric 

 gases. 2nd. But this clay has also another characteristic, it 

 is charged with common salt. If we place it on a filter, wash 

 it with distilled water, and evaporate the filtrate, a crop of 

 cubic crystals of common salt is obtained. Results of experi- 

 ments indicate 13 ounces of common salt per cubic yard of 

 clay ; the actual contents may somewhat exceed this propor- 

 tion, for it is well known that clayey matters will obstinately 

 keep in quasi-mechanical adhesion substances which would 

 be, excepting for the presence of the clay, easily removed in 

 solution in water. 



That an alkaline chloride will promote the rusting of iron 

 is instanced in the common iron-rust cement of the machinist. 

 A dense network of iron turnings, moistened with solution of 

 salammoniac, conforms to all the requisite conditions — per- 

 meability to air, the simultaneous presence of moisture, and 

 a suitable soluble alkaline chloride, provided as an oxygen 

 carrier. 



In the case described we have almost identical conditions, 

 with one exception. Our alkaline chloride is the chloride of 

 a fixed, and not of the volatile alkali ; we have chloride of 

 sodium instead of chloride of ammonium, and it is not so 

 easy to see how the chlorine forsakes its most intimate rela- 

 tions with the sodium to take up with the iron. The writer 

 cannot pretend to anything approaching a discussion of this 

 question on the basis of facts now presented. The subject is 

 certainly a matter of great interest, which has not yet been 

 fully discussed, and on which methodical experiment might 

 be profitably expended. At present the writer contents liim- 



c 2 



