MECHANICS AND USEFUL ARTS. 83 



■would fix a photograph, recommended the dyer to try that. The 

 trial was made ; when mixed with the hyposulphite, the blue be- 

 came a beautiful green, and, better still, a " fast color." This 

 was the origin of that brilliant dye commonly known as " Night 

 green," because of its remaining uimaistakably green in appear- 

 ance when seen by artificial light. Let it be remembered that 

 nearly all the new colors are extracted in some way from coal 

 tar; that the first was discovered not more than 13 years ago, 

 and that the annual value now manufactured is 1,250,000 i^ounds, 

 and it will be seen that in the industry created by these new 

 products there is an admirable example of the results of scientific 

 investigation. The best of it is that the field is inexhaustible ; 

 for many years to come it will yield a rich harvest of discoveries. 



REFINING VEGETABLE OILS. 



Mr. C. Michaud, of Honfleur, has discovered a new method of 

 refining oil, which will probably eclipse all those in general use 

 at the present day. This method has just been communicated by 

 M. Chevallier to the Societe d'Encouragement. While sulijhuric 

 acid is introduced into the oil in minute numerous streamlets, air 

 is blown into the oil so as to produce a great commotion in the 

 liquid and to fill it with air-bubbles. The mucilage contained in 

 the crude oil, being acted on by the acid, soon forms wiih the air 

 a voluminous layer of scum at the surface, which is skimmed off 

 as it forms. This insufflation of air is repeated several times, in 

 succession, and the scums cleared off every tune until the oil is 

 clarified. At this point of the operation it still retains free sul- 

 phuric acid. It is now run into a copper vessel, and steam is 

 forced through it until the oil has reached a temperature of 100" 

 C. The steam is then allowed to bubble through for half an 

 hour or an hour longer. After the oil has cooled down some 20° 

 or 30° C, which may be done artificially, it is run through an 

 ordinary filter. Two large refineries have lately been put up on 

 the " Michaud" plan, and the oil produced by them is so pure, 

 that the wick of a lamp burning it will not carbonize after many 

 days' usage. 



ON THE PENETRATION OF ARMOR-PLATES BY SHELLS WITH 

 HEAVY BURSTING CHARGES, FIRED OBLIQUELY. BY JOSEPH 

 WHITWORTH, LL.D., F.R.S. 



At the meeting of the British Association last year, Mr. Whit- 

 worth contributed a paper " On the Proper Form of Projectiles 

 for Penetration through Water," wherein he claimed for the flat- 

 fronted form of projectile made of his metal three points of 

 superiority over the Palliser projectiles. First: Its power of 

 penetrating armor-plates even when striking at extreme angles. 

 Secondly: Its large internal capaeiiy as a shell. Third: Its 

 capability of passing undeflected through water, and of penetrat- 



