The Artesian Wells of British Guiana. 105 



bably have been a good pumping well, Such a record, few, if any 

 countries, can claim, and we may confidently look forward to the same 

 percentage of artesian wells being brought in in the future. 



The system of drilling introduced here after the completion of the 

 first three wells drilled is called " The rotary system," the old type I 

 found in use here being the " Galician " or percussion system. Well- 

 drilling plants have to be selected with very great care and expert know- 

 ledge, to suit the varying conditions of districts and countries. In British 

 Guiana, the rotary type is very much superior to all others where it is 

 used on the coastal plains, but in the inteiior and away from the coast, 

 where rock would be encountered either on the surface or immediately 

 below, the percussion type of drilling would be applicable, and more suit- 

 able than the rotary system. The saving in working costs made here 

 with the introduction of the rotary system, was approximately $10 per 

 foot on completed wells, the actual costs being $3 and $13 respectively, 

 including all charges. (1914). 



The operation of the rotary system consits in rotating a column of 

 pipe carrying a fish tailed bit or drill on its lower end. Liquid mud is 

 forced by special pumps down the column of pipe and escapes from two 

 holes one on each side of the tail of the bit. The mud, not only drives 

 the cuttings to the surface, but the pressure exerted by the column of 

 mud prevents the hole from caving, and gradually lines the hole with a 

 thick coatiug of mud, which forms an inner shell. No casing is placed 

 in the well until the hole has been taken to the required depth, 

 when in connection with the proper strainers, it is rapidly lowered 

 into the hole to bottom. Water is then forced down the casing 

 and the mud washed out, when the well is then completed. If the 

 well is to be very deep, several sizes of casing may be used, in which case 

 the washing out process is only carried out in connection with the last 

 size of casing used. 



The question of the prevention of the choking of the artesian wells 

 has caused the Government much anxiety, but the euormous mine of 

 wealth in the underlying water sands, warranted and called for fresh 

 efforts and contrivances in order to get over the difficulty. After years 

 of trial and experimenting with every known device in order to check the 

 silting of the wells, the writer has at last improved on an existing method 

 which it is confidently hoped will solve the problem for all time, both 

 for deep and shallow wells. 



The first trial is being made at Nabaclis, close to the site of the 

 artesian well that was drilled there in 1915, but which has since been 

 abandoned on account of the collapse of the casing. 



The new well at the time of writing has been drilled down to 860' 

 to the lower water sands in 15" diameter hole, and has gone down again 

 in a 24" diameter hole to over 400', this size will be continued to the 860' 

 level, when the wall will be completed. For drilling such a large size 



