Gurney on Chemical Scie?ice. 303 



In Lecture V, we had hoped to have met him upon more equal 

 grounds, but to our utter dismay, a few paragraphs brought us to 

 a large organ, which our author undertook to build " some years 

 since, when a very young man," and which was " admitted on all 

 hands, to have a remarkably fine tone," though built " on theory, 

 for I had never seen the interior of one, till I had finished mine, 

 and knew nothing whatever practically of the construction of 

 them." This organ was combined with a piano-forte, and toge- 

 ther with the very pleasant anecdote brought in at p. 112, to 

 which we refer our musical readers, is somehow or other intended 

 to illustrate the doctrine of expansion, the strings of the piano 

 being it seems expanded, and its notes flattened by heat, while 

 those of the organ-pipes were affected in the opposite way. 



At p. 1 19 of this lecture, we are informed that " different colours 

 have different conducting powers in respect to heat" " black conducts 

 it the most readily, white the least so." This is quite new to us ; so 

 also are the following assertions (p. 121.) " Water, unlike all other 

 substances, is of a greater specific gravity when in a liquid than in a 

 solid state, which accounts for the lower parts of our rivers never 

 being frozen." Again, — " The particles of water, previously to their 

 assuming the state of a solid, conform to the general law of liquids 

 increasing in specific gravity, as they lose their caloric." This 

 gross error is the foundation of the blunders that abound in seve- 

 ral succeeding paragraphs. 



In the lecture on electricity, we are told at p. 133, that flannel 

 becomes positively electrical when rubbed on glass, but negative 

 when rubbed on sealing-wax, whereas the reverse is the case. 

 We are also told that the contact of two different metals excites 

 electricity in an eminent degree ; that this electricity is increased 

 by inducing a rapid change of surface, which maybe effected by 

 the action of an acid on the metals ; and that it is necessary that 

 the solution employed, be a good conductor of electricity. This 

 is a very summary theory of the pile ; and the difference between 

 its phenomena and those of the common electrical machine, is 

 equally hastily despatched. " In fact," says Mr. G., " the 

 common electrical machine differs from the galvanic battery, 

 iimply from its being defective in physical power, if we may so 

 express ourselves." At p. 13C, we are informed that the decom- 

 posing powers of electricity were first pointed out by Sir Anthony 

 Carlisle. 



" Another property of electricity," says our author, " is that 

 whenever the connexion is made between the two poles of a bat- 

 tery by a good conductor, it passes silently and without any visi- 

 ble effect." Now in the preceding paragraph, wc have just learned 

 that the said connecting wire is magnetic, and we suspect that 

 we have sometimes seen it red-hot, and sometimes fused. But 



