112 FLORIDA GEOLOGICAL SURVEY-THIRD ANNUAL REPORT.
nized the effect of local rains on their wells; others who have observed less closely recognize no such variation. That the rainfall is sufficient to supply the large quantities obtained has already been demonstrated.
FORMATIONS SUPPLYING THE ARTESIAN WATER OF EASTERN FLORIDA.
Aks explained in the chapter on geology the principal artesiar reservoir of the eastern part of Florida is the Vicksburg group of limestones. In some localities, however, formations lying above the Vicksburg group supply a flow, although the flow from these more shallow formations is rarely ever so strong as from the deeper or Vicksburg limestones.
DEPTIT OF THE ARTESIAN WATER.
The depth at which the artesian water is obtained is variable in different parts of the area. To find the depth for any particular locality it will be necessary to refer to the subsequent chapters in which the several counties are treated individually.
COST OF WELLS.
It has been only within the past few years that artesian wells have begun to supplant shallow, open dug wells in the rural districts. One cause of the rapid increase of artesian wells in these districts is the necessity of irrigation in order to safeguard trucking and general crops against droughts. Again, from a health standpoint, the water from these deeper wells is less liable to contamination than is the water from the shallower or surface wells.
The cost of an artesian well depends upon the depth to which it is necessary to drill, the size of the well desired, the amount of casing used and the character of the material that will probably be penetrated in drilling. With a knowledge of the nature of the underlying formations in a given area well drillers know approximately the time and labor it will take to complete a certain size well. In such an instance it is frequently the case that a well is completed for a stipulated amount regardless of the depth. It is more customary, however, to let a contract for a certain size well at a given price per foot. These prices vary in different sections of the state but on the average two inch wells are sunk for from $I.OO to $1.25 per foot; three and four inch wells from $1.50 to