Chemicdl Science. l69 



destructive animal is never known to penetrate the material in 

 the slightest degree. The hair, or hair and wool, is pre- 

 pared for felting by the operation of dressing or bowing, as 

 in the practice of hat-making, and is filted in the usual manner. 

 Sheets or portions, thus felted, are dipped into the melted tar 

 and pitch, certain stated proportions to each other, and then 

 undergo a slight compression to take away the extraneous or 

 dripping quantity of the material ; they are then exposed for a 

 short time to air to dry and cool, and are considered fit for 

 use. — New Monthly Magazine, July, p. 347. 



3. The Apograph. — This is a newly-invented instrument for 

 copying drawings upon paper, copper, or any other substance 

 capable of receiving an impression, and upon any scale. It is 

 said, the arts furnish no instance of an instrument resembling 

 it either in its operation or appearance, except, perhaps, the 

 pantograph, from which it differs in the position of the beam in 

 an horizontal plane, and in the addition of a counterpoise to 

 return the hand when the beam is not vertical, and in other re- 

 spects. Mr. Smith, of Ayr, is the inventor. 



4. New Madder Lake. — Mr. Field, after seven years of much 

 labour, has prepared a lake from madder which, in point of 

 brilliancy and strength both for oil and water-colours has, till 

 within a short time, hadjiothing comparable to it in the arts, 

 it is also of a very durable nature. — New Monthly Mag. Sept. 



5. Contamination of Salt for Manufactories. — The following 

 question having been proposed to the Academy of Sciences by 

 the French Ministry : " What are the processes to be adopted 

 in contaminating common salt without injury to the soda ma- 

 nufactories, which will not permit of its re-appropriation to the 

 uses of common life by any secret process, or at so little ex- 

 pense, as to make the chances or the profits encourage fraud ?" 



The academy in answering say, that it is impossible to re- 

 solve the question because of the high price of salt, but that 

 the following means will render the fraud the most difficult. 



1. Colour the salt by -^^^ of wood charcoal. 



2. Infect it by ^^i^^i^ of oil, distilled from animal substances, 

 or ^y -dr, of tar. 



3. To make the mixture in the magazines. 



II. CuKMicAL Science, 

 § Chemistry, Electhicity, Magnetism. 



1. On the Analysis of Alkaline Minerals, by M. Berthier. 



M.Borthicr, remarks in Ills paper on this important part of Analyti- 

 cal Chemistry, that the use of barytcs is inconvenient from the 

 necessity there is of repeatedly heating it with the mineral to be 

 analyzed before the action te complete, and uncertain from the 



