658 PHILOSOPHICAL TRANSACTI0K8. [anNO I694. 



columns are some of them 2 feet in diameter. Yet this disproportion of bulk 

 is not so considerable a difference, since we observe that nature affects the like 

 disparity in other of her works, and those too nearly allied, and evidently of 

 the same tribe or family. 



But nothing among all the fossil tribe, that I have seen or read of, comes so 

 near in all respects, in its formation, substance, size, way of growth, or manner 

 of standing, &c. to our columns, as the lapis basaltes misenus, described by 

 Kentmann, in Gesner de Figuris Lapidum, from whence Boetius takes both his 

 figure and description, of which he says there is a large bed within 3 miles of 

 Dresden in Saxony, and described in such words, that he could hardly have 

 better described the collection of pillars, that make the Giant's Causeway, seem- 

 ing as if he had seen them on the place; only I find this difference between 

 them and the Misnean basaltes, that its columns were one entire piece from top 

 to bottom, and some of them four-squared ; whereas our Irish basaltes is com- 

 posed of columns, whereof none are four-squared, and all of them divided into 

 many joints.* 



Account of the Evaporation of Water, as experimented in Gresham College in 

 the Year \6Q3 ; with some Observations. By Edm. Halley. N°212, p. 183. 



I caused an experiment to be made of the quantity of vapour arising simply 

 from the warmth of the water, without being exposed either to sun or wind, 

 which has been performed with great care and accuracy by Mr. Hunt, operator 

 to the society : having added together the evaporations of the whole year, I 

 find that, from a surface as near as could be measured of 8 square inches, there 

 evaporated during the year, 16292 grains of water, which is 64 cube inches of 

 water, and that divided by 8 inches the area of the water's surface, shows that 

 the depth of water evaporated in one year amounts to 8 inches. But this is 

 much too little to answer to the experiments of the French, who found that it 

 rained 1 9 inches water in a year at Paris ; or those of Mr. Townley, who, by 

 a long continued series of observations, has sufficiently proved that in Lan- 

 cashire, at the foot of the hills, there falls above 40 inches of water in a year. 

 Whence it is very obvious, that the sun and wind are much more the causes of 

 evaporation, then any internal heal, or agitation of the water. The same ob- 

 servations also show an odd quality in the vapours of water, which is that of 

 adhering to the surface that exhaled them, which they clothe as it were with a 



* Then follows a short postscript wherein are pointed out some errors into which the author of the 

 account of the Giant's Causeway, inserted in No. 199, of the Trans, [p. 529 of this vol.] had fallen; 

 the liubstance of which posttcript u given in the note belonging to that account. 



