NATURAL PHILOSOPHY. 131 



tricity developed is that termed " resinous." But if the strip be folded 

 double and rubbed, the upper side exhibits "resinous," and the low- 

 er side "vitreous," electricity, and the t\vo extremities attract each 

 other. 



A postscript describes an improvement on this machine, in which a 

 thicker description of band is used. The two rollers are of equal 

 size, and the rubbers, which are brushes of bristles, four in number, 

 are placed outside the band and opposite the axis of each roller. A 

 double conductor, connected by a curved brass rod passing over the top 

 of the machine, is applied, similar in form to the conductor of the plate- 

 glass machines ; and there is a tightening apparatus, to correct the ex- 

 pansion and contraction of the band. The electricity given off ap- 

 pears to be of higher intensity, ar.d, under favorable states of the 

 weather, nearly as much in quantity as that of an ordinary plate-glass 

 machine. 



APPLICATION OF THE ELECTPtOTYPE PROCESS TO THE PRESER- 

 VATION OF INSECTS, FLOWERS, ETC. 



AT the meeting of the Society of Arts on Dec. 12, 1849, Mr. 

 Highton drew attention to Capt. Ibbetson's application of the process 

 of electrotyping to the preservation of the form of natural objects, 

 such as animals, insects, plants, &c. The process is as follows. 

 As it would be impossible to coat the whole surface of the object with 

 plumbago (which is the ordinary mode of preparing non-metallic sub- 

 stances for the process of electro-deposition), on account of the extreme 

 delicacy and minuteness of some of the parts, the insect, leaf, or 

 flower is first steeped in a solution of phosphorus, and afterwards in a 

 solution of nitrate of silver ; when the phosphorus causes the silver to 

 precipitate upon the object, and thus form a very thin metallic coating 

 over every part of it. Upon this a thicker deposit of metal is obtained 

 by the electrotype process, after which two or three small holes are 

 made through the coating, and the specimen is subjected to heat pow- 

 erful enough to drive off all the moisture. London Journal of Arts, 

 Feb. 



CONDUCTING PO\YER OF ACIDS. 



IN a memoir presented to the French Academy on " the conducting 

 pow r er of acids and the development of electricity in the combination 

 of acids and bases," M. Matteucci states the following observations 

 and conclusions. It is proved incontestably, that there is a develop- 

 ment of electricity in the combination of nitric acid and potash, even 

 when there is no metal in the circuit, and that the current is directed 

 from the alkali to the acid in the point where the chemical action is 

 the most intense. However little the nature of the acids and alkalies 

 which compose this quasi battery is varied, we easily perceive that 

 nitric acid and potash form the strongest electric combination of this 

 sort. 



In comparing the conducting po\ver of acids and alkalies as affected 



