Miscellanies. 393 



matter ; but that, on the contrary, by confining aud restraining 

 the electrical discharge within a very narrow limit, the application 

 of a small rod or wire of metal to a given portion of a building is 

 in reality highly objectionable. 



Rotary Pump. — A new description of rotary pump has been 

 invented. The machine consists of a cylinder, around the axis of 

 which work four vanes, connected with the axis by rings, after 

 the manner of a compass or rule joint, and having their edges 

 completely in contact with the internal surface of the cylinder. 

 Their middle points are connected by links to four pins or bosses, 

 symmetrically situated on the inner surface of a disc, working in 

 an eccentric recess in the top of a cylinder. The dimensions of 

 the parts being properly adjusted, the effect of this arrangement is 

 to cause the space between any of the vanes to be maximum when 

 they are on that side of the cylinder farthest from the centre of 

 the recess, and minimum when they are on the other side. 



Effect of Metals on the Hair. — M. Stanislas Martin has pu- 

 blished, in the " Bulletin de Therapeutique," the curious case of 

 a worker in metals, who has wrought in copper only five months, 

 and whose hair, which was lately white, is now of so decided a 

 green that the man cannot appear in the street without imme- 

 diately becoming the object of general curiosity. — He is perfectly 

 well, his hair alone being affected by the copper, notwithstanding 

 the precautions taken by him to protect it from the action of the 

 metal. Chemical analysis shows tliat his hair contains a notable 

 quantity of acetate of copper, and that it is to this circumstance 

 it owes its beautiful green color, which is most singular and re- 

 markable. 



The Discoverer of Gutta Percha. — The discoverer of this ins- 

 pissated sap of an Indian tree — now so extensively used in the 

 arts and sciences — was Dr. Montgomerie, of the Indian medical 

 service, and this only in the year 1845, although many of the 

 countries producing the article have been in European occupation 

 for above 300 years. The mode in which the discovery was made 

 is worth mentioning. Dr. M. observing certain Malay knives and 

 kris handles, inquired the nature of the material from which they 

 were made, and from the crude native manufacture inferred at 

 once the extensive uses to which the gutta percha might be put 

 in the arts of Europe. He purchased a quantity of the raw ma- 

 terial, sending from Singapore part of it to Bengal and part to 



