506 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



Other side, after taking off the nut, is resisted by the wooden 

 thread. 18 C, June 1, 1873, 686. 



INSTKUMENT FOR TESTING MINEEAL OILS. 



A simple instrument for testing the quality of the petrole- 

 um oils has recently been brought to public attention, and 

 though by no means accurate enough in its indications for 

 scientific uses, it answers very well for an approximate method 

 of determining the inflammability of such oils; and is so 

 simple in its action that it requires no skill to operate, on 

 which account it may prove useful in the household. It 

 is called " Blair's Apparatus for Testing Hydrocarbon Oils," 

 and is constructed upon the principle that the expansion 

 and contraction of the several hydrocarbon oils under dif- 

 ferent temperatures is in a direct ratio to the percentage 

 of naphtha or other inflammable liquids contained in it ; an 

 adulteration of a safe oil with naphtha increasing its rate 

 of expansion to such an extent as to render the same easy 

 of detection. The instrument is constructed, therefore, to 

 enable one to compare the expansion of any oil to be tested 

 with that of a standard safe oil both being subjected to the 

 same degree of heat. The instrument consists of a case 

 holding two bottles, furnished with glass tubes of equal bore. 

 In one of these bottles is placed the oil which serves as the 

 standard of comparison ; and in the other, to the same height 

 in the tube, is placed the oil to be tested. The bottles are 

 mounted upon a wooden support, suitably graduated. To be 

 used, it is inserted in a vessel of water, of a temperature of 

 110 (the legal burning-point of safe oils), and the inference 

 as to the safety or danger of the sample is judged from the 

 cautionary words upon the support behind the tubes. To 

 those who prefer not to test a sample of oil b}^ the simple 

 plan of attempting to ignite a few drops of it in a saucer with 

 a match, the apparatus above described will be of service. 



ILLUMINATION BY MEANS OF ELECTllICITY. 



Dr. Crookes, of London, has recently published an interest- 

 ing article showing the progress made in electric illumination 

 during the past few years. 



The first great step in the series of inventions was that 

 made by Wilde, in the invention of his form of the magneto- 



