Intelligence and Miscellaneous Artictes, 



this property in their normal state, or at least in the condition m 

 which they are found in commerce ; others appear destitute of this 

 property, and it is upon these differences that I propose a means of 

 distinguishing them. 



My method of experimenting is to take slips of lead test-paper 

 and hold them over a bottle of hydrosulphuret of ammonia until it 

 acquires a uniform brown tint ; I then let a drop of the oil to be 

 tried fall upon the paper so prepared, and hold it over the plate of 

 the furnace to quicken the process and evaporate the excess of oil. 

 In this manner the following results were obtained : — 



A) ,. 



.Turpentine and oil of lemons offer, perhaps, the most marked 

 contrast ; the one instantly destroys the colour, the other produces 

 a scarcely perceptible effect, and that only after frequent repetitions 

 of the process. nfc 



We have thus in our power to detect with ease any adulteraticB^ 

 of the latter oil with the former. I- ' 



One or two per cent, may be detected thus, and with four per ceiiti 

 the effect is almost as strongly marked as with the pure oil of tur- 

 pentine. 



When the quantity of the last-mentioned oil is very small in the 

 sample to be examined, it is as well to repeat the addition and the 

 subsequent heating two or three times. 



I enclose a specimen of the effect of oil of lemon adulterated with 

 two and four per cent, of turpentine ; also a slip showing the action 

 of the oils in the pure state, and am. 



Gentlemen, -^ 



^our very obedient Servant, 



C. Greville Williams. 



:4^ 



I^btE ON INDUCTIVE ELECTRICAL MACHINES, AND ON A READY 

 Y* MEANS OF INCREASING THEIR EFFECT. BY M. FIZEAU. |^^ 



The electrical machines which have been constructed of late years 

 on the inductive principle are now well known ; the constancy and 

 regularity of their effects, as well as the facility of their employ- 

 ment, present marked advantages, which render these new machines 

 preferable in some cases to those of the old construction. 



Having undertaken some new experiments on the rapidity of the 

 propagation of electricity, especially with the view of comparing in 

 this respect electricity of tension with galvanic electricity, I found 

 the employment of this apparatus very suitable for the purpose, but 



Phil. Mag. S. 4. No. 35. Hu^h Vol. 5. 2 N 



