This is the third bulletin of the following series: 1. Oil and its geology. 2. Prospecting for oil. 3. Drilling for oil. 4. Laws pertaining to oil. It is not intended that this bulletin should serve as a book by which! the prospector could undertake the drilling of oil wells, but only to show that drilling is a profession by itself. Drilling for petroleum should in all cases be undertaken by the expert and also under contract, if possible. The conditions which are encountered and which have to be overcome are often great and tax the ingenuity of the expert driller. For this reason, therefore, this bulletin is written to show the oil prospector what is being undertaken when drilling for oil is commenced, and the conditions, troubles and set-backs which may be encountered. 8 p.