354» Mr. Lubbock on the Variation of the 



quarters of an ounce, oil of turpentine half an ounce, vermi- 

 lion one ounce. Powder together the lac, kauri, and resin ; 

 add the vermilion, and then the turpentine. Let them re- 

 main a few days in a well-covered vessel, then melt them 

 together in a very gentle heat. The kauri will liquefy in this 

 composition ; it burns well, drops freely, and takes a fine im- 

 pression. But it does not always adhere firmly to the paper; 

 a very serious defect, of which the cause or remedy has not 

 hitherto occurred to me. The same thing sometimes hap- 

 pens with sealing-wax made of the usual ingredients, but less 

 frequently than with kauri. 



Another purpose for which its brilliant inflammability and 

 comparative infusibility qualify it, if it come in largely and 

 cheaply, is gas light. A modification of the oil gas apparatus 

 would work it, and the material being supposed at one-fourth 

 the price of oil, whilst the original outlay in laying pipes, &c. 

 would be in the same small proportion as for oil gas, it would 

 stand a fair chance in competition with coal gas, and be much 

 less disagreeable in dwelling-houses than any gas hitherto 

 employed. 



As to its officinal employment in medicine and surgery, 

 time and experience only can indicate them. External ap- 

 plication seems most suited for it ; its masticatory employment 

 is not very likely to be adopted in Europe. 



The older transparent pieces do best for sealing-wax, for 

 which their colour is not an objection. The recent white are 

 most suitable for varnish, being first deprived of moisture by 

 drying over a sand- or water-bath, when they become trans- 

 parent, still remaining colourless. 



XXXVIII. On the Variation of the Arbitrary Constants in 

 Mechanical Problems* By J. W. Lubbock, Esq,^ FJi.S. 



[Continued from vol. xi. p. 495.] 



T^HE methods I employed with reference to the equations 

 -■- of motion expressed in terms of rectangular coordinates 

 X, y, 2-, are very easily extended to the more general case 

 when the equations of motion are in the well-known form 



