No. 144.] ■ 533 



1st. Excess of moisture, even on lands not evidently wet, is a 

 cause of fogs, mists and damps 



2d. Dampness serves as the medium of conveyance for any de- 

 composing matter that may be evolved, and adds to the injurious 

 effects of sucli matter in the atmosphere; in other words, the ex- 

 cess of moisture increases and aggravates atmospheric impurity. 



3d. The evaporation of the surplus moisture lowers teuipera- 

 ture, produces chills, and creates the sudden fluctuations, by which 

 health is injured. 



Where there is a great accumulation of surplus moisture^ having 

 animal or vegetable matter in solution or suspension, the injury 

 to the public health is so considerable, as to amount to a nuisance, 

 requiring authoritative intervention of the civil authorities. These 

 evils are found in thegreatest intensity in low- lying town districts, 

 in valleys near rivers, or on sites below high water mark. In 

 draining it is necessary to find the springs first, as they are the 

 source from whence our trouble comes ; they may be viewed as 

 artesian wells, and may be explained on the same principles. 

 Rain falling on hills runs over the surface to all lower levels. If 

 in its progress it passes over clay or impervious rock, it cannot 

 sink ; if it encounters a pervious layer, such as gravel, it at once 

 sinks and flows in the interstices as in a pipe, until it reaches an 

 impervious layer, and, being unable to descend, it comes to the 

 surface and forms a marsji. The rule to be followed when dealing 

 with such cases, is to cut of the water as near its sources as pos- 

 sible, by running a drain along the line of out-crop, or in other 

 words, between the wet and the dry, or a little below the com- 

 mencement of the marsh. The water, so intercepted, maybe 

 conveyed to lower levels. The principle is, 



1st. Upon discovering the main spring, without which nothing 

 can be done, and 



2d. Upon obtaining the level of that spring, and finding its 

 underground bearings, for, if you should be so unfortunate as to 

 cut ^three feet beyond the line of the spring, you cannot by any 

 chance reach the water, that issues from, it; by discovering that 

 line, you can cut off" the spring with certainty, and drain the land 

 in the must effectual and cheapest manner. 



