VOL. IV.J PHILOSOPHICAL TRANSACTIONS. 419 



The highest place of the whole channel was well enough known, which was 

 to be the pointy called the point of division or separation. Nature herself 

 sufficiently pointed at it by the spring of Grave, which partly runs towards the 

 Ocean, and partly towards the Mediterranean : and it is near this place where 

 the great basin is made to receive the waters that are to run both sides of the 

 channel. But this water being not near sufficient, it was necessary to find out 

 others, that might be high enough to fall into the said bason, and copious 

 enough to keep it always full, and to furnish for the sluices of those two parts of 

 the great channel. 



It appeared also that this plenty of waters could only be had from the Black 

 Mountain, distant enough from it; but it did not appear how this could be 

 effected. In short, it is this wherein the greatest difficulty of the whole work 

 consisted. For we must know, that there are many springs issuing from the 

 higher part of that mountain, and that among the rest there are five great ones, 

 which make as many small rivers, that are never dried up, but run along the 

 hillocks of this mountain, and fall together into the river Fresqueil, but so far 

 above the said point of separation, that that remoteness would render them ab- 

 solutely useless, it not being possible to make them remount. Wherefore to 

 make them serve for this purpose, it was necessary to interrupt their natural 

 course from north to south, and to give them a contrary one, from east to 

 west, by digging a conduit for them across the mountain, through places 

 which are all steep rocks and horrid precipices. There was then a necessity to 

 make those five rivers run, the first into the second, and the second into the 

 third, fourth and fifth, and to re-unite them all in the deriving channel, 

 which at last carries them to the point of separation for the end above- 

 mentioned. 



Some Considerations relating to Dr. Wlttie^s Defence of Scarborough 

 Spa; concer?iing a Salt Spritig' in Somersetshire; and a Medical 

 Spring in Dorsetshire. By Dr. Highmore, in a Letter to Dr. J, 

 Beale, at Yeovil in Somersetshire, N" 56, p. 1128. 



Dr. Highmore doubts of the existence of alum in the Scarborough spa. He 

 remarks, that from a wine quart of the salt spring at East Chenock, in Somer- 

 setshire, (above 20 miles from the sea) he obtained by evaporation near 80 

 grains of salt ; though this experiment was made at a time when the spring 

 Was less salt than usual, by reason of the late rains. He supposes that the 

 Farrington waters in Dorsetshire, which are called chalybeate, are impregnated 

 principally with vitriol or salt of iron ; for he found that by dissolving two 



3 G 2 



