438 Miscellaneous Intelligence. 
themselves; they are then transferred to a piece of fine linen and 
pressed. The liquid is collected on glass and left to evaporate, when a 
pellicle forms like that of collodion. It should be used within 24 hours, 
as it afterwards becomes spongy and insoluble in water, alcohol and 
ether. 
Impression by heat, or Thermotypy.—This process proposed by M. 
Abate is very simple, and is based on the destructive action exerted by 
chlorhydric acid on organic substances. Suppose for example we have 
a slice of wood of which we wish a faithful impression. The wood is 
cotton cloth, or white wood, in a press, and a blow struck. T i 
pression is at first invisible; but on exposing it to a strong heat, It 
gradually appears, and exhibits a perfect picture of the wood. 1 
operation may be repeated indefinitely. For oak, maple, hazel, &c., 
the picture is of the color of the wood ; but for mahogany, rose W 
and many others, the color is modified, and if a perfect colored picture 
is desired, it should be taken on a previously prepared tint 0 the re- 
quired kind. 
It occurs to us that, by taking an impression on a plate of zinc, tin, 
ght 
beneath the water three quarters of an hour, after which he came UP 
to breathe and rest; his light was an oil lamp, placed on the: head of 
the diver, and fed with air proceeding from his respiration, whence, tt 
and at the same time it is strong and well secured hermetically, to Te- 
sist a pressure of 50 to 60 meters of seawater. It consists of a cy! 
i 
nearly parallel. As the lamp is moveable, the diver walks about with 
it and it where he wishes to make any search ; and as it is only 
* 
