OUR POLYTECHNIC. 305 



same material, is the cocoon or cell of a caterpillar of the Puss Moth. The 

 next is that of a Goat Moth the winter abode of its long-lived larva in the 

 heart of a tree ; a portion of the wood wherein it is embedded, being cut away, 

 shows its fabric, a cloth-like substance of mingled silk and raspings of wood. 

 On the upper shelf of all are three tools, used by insect artificers. To the left 

 are the powerful toothed jaws, constituting chisel, plane, and forceps of a Mason 

 Wasp. Next, in the centre, is the compound tool, consisting of an auger and 

 a pair of files, used by the Tree-hopper, to make grooves in branches for the 

 reception of her eggs ; and to the right, is a portion of the saw used by Saw- 

 flies for a similar purpose. 



A NEW GALLERY OF PRACTICAL SCIENCE. 



ADIES and Gentlemen of a mechanic turn, 

 we can introduce you to a new theatre of ex- 

 hibition, where ingenious mechanisms, arts, 

 and manufactures are in daily operation. 

 There, without payment of a shilling, you 

 may look upon diving-bells and balloons see bodies pro- 

 pelled through water by the strokes of an internal piston 

 examine the models of a life-boat and a raft observe the effect 

 of cleverly-constructed buoys behold in practice, or in their 

 finished productions, the crafts of masonry, carpentry, spin- 

 ning, weaving, and paper-making see the operations of and 

 the implements for boring and tunnelling, the exercises of 

 rowing and diving, with various other clever and curious per- 

 formances, of which the Polytechnic can do no more, and in 

 many instances does less, than display the parallels. Should 

 you even be of the number who frequent the above-named 

 gallery for its music rather than its mechanisms, for its pictures 

 rather than its philosophy, our theatre lacks not something to 

 suit your humour. 



The use of that most simple yet most powerful of instru- 

 ments, the wedge, could have been suggested by an operation 

 commonly performed by every species of bee ; yet he who first 

 hit upon this wonder-working implement would have no doubt 



