BY ROBERT L. JACK, F.G.S., F.R.G.S. 67 



last twelve months, must be carried out for some years before 

 we can arrive at the relations between the rainfall and the 

 activity of the wells. It must be mentioned, by way of caution, 

 that some of the wells obviously owe their stoppage to faults in 

 tubing, and others to the caving-in of the strata. The obser- 

 vations are rendered necessary by the fact that strata in which 

 the grains or granules are massed together with varying and 

 unknown degrees of compactness must conduct water (owing to 

 friction) at a rate different from what would be the rate in the 

 theoretical open tube. It may take one, two, five, twenty, or a 

 hundred years for a given drought to affect any particular bore ; but 

 if corresponding curves can be established by observation between 

 rainfall on the one hand, and the output of the bores on the 

 other, we shall have a law by which we can predict in any given 

 year what will be the flow of the bores — barring, of course, such 

 accidents as decay of tubing, filling up with deposited mineral 

 matter, and caving-in of the strata. It is now well known to 

 borers that the nearer they are to the edge or intake of the basin, 

 the less will be the chance of a heavy supply, and the greater 

 will be the chance of an intermittent supply, the obvious 

 explanation being that the head of water in these cases is apt 

 to fall to or below the level of the bore. At the January 

 meeting Mr. Thomson advanced an argument against the 

 submarine leakage, which I am able to quote verbatim : — '• I 

 am strongly of opinion that the pressure of the higher specific 

 gravity waters of the ocean would prevent any remarkable 

 leakage at anything like considerable depths." At the May 

 meeting, when I was present, Mr. Thomson further expounded 

 and Mr. Gregory confirmed this view. Given a sufficiently 

 elevated "head" of fresh water, connected by a tube with the 

 salt water of the ocean, an equilibrium, depending on the slight 

 difference between the specific gravities of fresh and salt water, 

 would inevitably be established. This is one of the simplest 

 axioms of hydrostatics. If, instead of salt water, the ocean 

 were filled with glue of a tenacity sufficient to protect the 

 submarine outlet of the strata from the pressure due to the head 

 of water at the outcrop, then we coald understand how the 

 strata could fail to be periodically emptied, and prepared to receive 

 further contributions from the rainfall ; but on no other 



