NATURAL PHILOSOPHY. 153 







led, at first, to the supposition, that they were composed of two sorts of iron; 

 but besides the utter improbability of this, the contrary was proved by an ex- 

 amination, which led to the inference that the extremities of the piles having 

 been charred, the straps of iron closely wedged between them and the stratum 

 in which they were imbedded, must have been subjected to a galvanic action. 

 which, in the course of some six or seven hundred years, gradually produced 

 the effects recorded. 



ELECTRO-CHEMICAL PAPER FOR TELEGRAPHIC PURPOSES. 



M. Afaisonneuve has recently presented to the French Academy an electro- 

 chemical paper for telegraphic purposes, which seems to fulfill all the condi- 

 tions necessary for complete success, which he enumerates as follows : 1st. 

 cheapness; 2d. sufficiently sized to take annotations in ink; 3d. sufficiently 

 humid to be a conductor, yet without excess, so as to receive these annota- 

 tions ; 4th. slightly acid, to increase its conductibility, yet not enough to afiect 

 the metals which it touches ; 5th. easily decomposable by electricity ; 6th. 

 giving, by means of this decomposition, a deep-colored, insoluble and stable 

 salt ; 7th. of so simple a composition that it can be prepared at the stations 

 themselves, if found advisable ; 8th. not requiring any peculiar kind of paper 

 pulp ; 9th. of an easy and simple composition, not requiring the proportions 

 of the salts to be very exact. 



The formula for the preparation of this paper is as follows: "Water, 100 

 parts; crystallized nitrate of ammonia, 150; yellow cyanide of potassium and 

 iron, 5. By using 150 parts nitrate of ammonia this paper acts well in the 

 summer, and without requiring to be kept from the air. A short immersion 

 in water will remove any excess of these proportions. It may be prolonged 

 without injury to the clearness of the characters. 



COMPASS VARIATIONS IX THE MERCANTILE MARINE. 



Colonel Sabine, of England, in a recent publication on the danger to which 

 vessels are exposed from compass variations, expresses the opinion that in all 

 large ports, at least, in which vessels are equipped, a competent person should 

 be appointed, whose duties should be to select in every ship an advantageous 

 position for a standard compass, combining the two requisites in such selection 

 of a manageable local attraction, and of convenient access for navigating the 

 ship ; to determine experimentally the local deviations of the standard com- 

 pass in different azimuths ; to instruct the master how to repeat the same on 

 future occasions : and to see that he rightly and thoroughly understands the 

 deduction of the true magnetic courses from those of the standard compass, 

 and of the course by the standard compass corresponding to the true course 

 which he desires to steer. The performance of these duties on the part 

 of the person so appointed to be imperative, at least in all cases of iron ships 

 and steamers, by a regulation that no such ship should be permitted to leave 

 the port until a certificate should be produced that they have been duly per- 

 formed. 



7* 



