12 Experimental PhilosopJiy. [Lecture 2. 



traded by it. On this circumstance an amusing 

 story in the Arabian Nights Entertainments is 

 founded. A' rock of loadstone (adamant it is 

 called by an error of the translator) is supposed 

 to exist in a certain part of the ocean ; and when 

 a vessel approaches it, all the iron bolts and nails 

 are attracted by it, and the vessel consequently 

 goes to pieces and is wrecked. 



But I can show you a still more surprising 

 (and to most of you, I dare say, new) effect of 

 attraction. I take two phials, which I number 

 1 and 2, filled each of them with a fluid perfectly 

 colourless ; you see they appear like clear water : 

 on mixing them together the mixture becomes 

 perfectly black. I take another phial, No. 3, 

 which contains a colourless fluid also, and I pour 

 it into this black liquor, which again becomes 

 perfectly clear, except a little sediment which re- 

 mains at bottom. Lastly, I take the phial No. 

 4, containing also a liquid clear like water, and 

 by adding a little of it, the black colour is re- 

 stored. 



All this may appear to you like magic, but it 

 is nothing more than an effect of attraction. Phi- 

 losophy keeps no secrets, and I will explain it to 

 you. The colourless liquor in the phial, No. 1, 

 is water in which bruised galls have been steeped 

 or infused ; that in No. 2, is a solution of sul- 

 phat of iron, the name now given to the copperas 

 or green vitriol of commerce. In plain terms, 

 it is water in which common copperas or green 



