CANAL. 95 



shall not be deterred by my acknowledged incom- 

 petency from gratifying your wishes. 



It appears to me that in seasons of great heat, 

 a change of water is as essential to health oii 

 canals, as a change of air is in houses. Fresh 

 water is as important as fresh air y|pd whenever 

 this is neglected, the banks of cansff will exhibit 

 the same diseases as the country in the vicinity of 

 any other stagnant waters. A considerable part 

 of this canal runs through a region of gypsum 

 which it is well known consists generally of 32 

 parts of lime, 46 of sulphuric acid, and 22 of 

 water. These component parts may indeed dif- 

 fer in different species and varieties, and gypsum 

 sometimes contains foreign ingredients, such as 

 alumine, iron and silica. The principal consti- 

 tuent, being sulphuric acid, and this substance, 

 which is commonly called oil of vitrol, and which 

 is derived from sulphur and oxygen, being neces- 

 sarily unwholesome, will communicate its quali- 

 ties to the canal in the most deleterious manner, 

 if the water is left in a stasje of stagnation. Be- 

 sides this, the water will by frequent change be 

 supplied with fresh solutions of lime, which will 

 have a tendency to neutralize the miasmata of 

 vegetable putrefactions. In old settled countries, 

 yapid streams are an indication of salubrity, bur 

 in this western region, where the waters are im- 



