398 report— 1878. 



Between the years 1867 and 1871 the salts had increased 19 - 63 per 

 cent., and between 1871 and 1878 they had further increased 4064 per 

 cent. The rate of increase between 1867 and 1871 was 4 - 91 per cent, per 

 annum, and the rate between 1871 and 1878 was 5 - 81 per cent, per 

 annum. The difference is to be accounted for by the larger quantity of 

 water per day that has been pumped out of the well. Since the year 

 1871, 295,200 gallons daily have been taken out of the well, which is 

 equal to 88-| million gallons per annum. 



The well had been in use for many years prior to 1867, but in that 

 year it was deepened, and a bore-hole made to increase the supply of 

 water. 



The inference drawn from this, and like results obtained elsewhere, 

 was that the Bunter sandstone rock filtered salts out of sea water. 



In the months of March, April, and May this year, I submitted the 

 inference to the test of the experiment now to be described. 



I selected four cubes of Bunter sandstone from the pebble beds in a 

 quarry in Everton. Each cube measured accurately 12 in. by 12 in., by 

 13 in. high. The top surface of each cube was dished out 9 in. by 9 in., 

 by 1 in. in depth, to form a receptacle into which water could be 

 poured. 



Three of the cubes were thoroughly dried in air, and placed one above 

 the other in a frame, so that the water poured on the dished part of the 

 upper one would, after passing through it, drop into the dished top of 

 the second cube, and after passing through the second would drop on to 

 the third, and after passing through the third cube, would drop into a 

 bottle placed underneath to receive the final filtrate. 



The first trial showed the water followed the planes of stratification 

 before passing through the whole thickness of the cube. That cube was 

 therefore rejected in the experiment. The second trial showed that the 

 dished part of the cube was cut on the edge of the planes of stratification, 

 and there was also some evaporation from the sides. The water passed 

 through this cube in eighteen hours. This cube was also rejected on 

 account of the defects which I have stated. 



In order to prevent leakage through the sides and evaporation, I coated 

 four of the sides of the two remaining cubes with black varnish, and 

 closely covered them and the frame holding them with oil-cloth ; by 

 these means the water passed through their mass under conditions favour- 

 able to give accurate results. I also cut three cubes measuring 1^ in. 

 on each side from the same stones (exhibited at the Dublin meeting) to 

 ascertain the capacity of the sandstone for storing water, the storage 

 space being the aggregate of the microscopic interstices which exist 

 between the grains of quartz, of which the sandstone is composed, and 

 also of the faults and fractures. 



The mean result obtained from the three cubes was that each cubic 

 foot of sandstone would store 0"733 gallon of water. 



Let us now consider the experiment on filtration. 



I took from the River Mersey off the Rockferry slip, at half tide ebb, 

 fifteen gallons of water, and allowed the muddiness to subside before 

 filtering through the stone. A portion of the water was then carefully 

 run in small quantities into the dished part of the first cube, until it 

 began to drop from the bottom ; and when two fluid ounces had passed 

 through, I carefully analysed the quantity of the chlorides left in the 

 filtrate, and found that 80"8 per cent, had been removed by the filtration. 



