Mechanical Science. 143 



of a process of this kind, which, according to Mr. Perkins and 

 Mr. Gill, is to be practised in the following manner : — The 

 borax is to be dried in a crucible, not till it fuzes, but till it 

 forms a white crust ; then powdered and mixed with the iron 

 filings : the joint is to be made bright and moistened with a 

 solution of the sal ammoniac ; then the mixture is to be made 

 into a thick paste with water, and placed along the inside of 

 the joint, and the whole heated over a clear fire till the cast- 

 iron fuzes. — Tech. Rep. iii. 110. 



17. New Form of the Voltaic Apparatus. — Mr. Pepys has 

 constructed, at the London Institution, a single coil of copper 

 and zinc plate, consisting of two sheets of the metals, each 

 fifty feet long by two feet broad, having therefore a surface of 

 200 square feet ; they are wound round a wooden centre, and 

 kept apart by pieces of hair-line, interposed at intervals be- 

 tween the plates. This voltaic coil is suspended by a rope 

 and counterpoise over a tub of dilute acid, into which it is 

 plunged when used. 



It gives not the slightest electrical indications to the electro- 

 meter ; indeed, its electricity is of such low intensity that well- 

 burned charcoal acts as an insulator to it ; nor does the quan- 

 tity of electricity appear considerable, for it with difficulty 

 ignites one inch of platinum wire of -^ inch diameter. "When, 

 however, the poles are connected by a copper wire ^ inch dia- 

 meter and 8 inches long, it becomes hot, and is rendered most 

 powerfully magnetic, and the instrument is admirably adapted 

 for all electro-magnetic experiments. Dr. Wollaston's well- 

 known and curious arrangement of a single pair of plates, may 

 justly be called a Calorimotor ; and to Mr. Pepys's coil we may 

 apply the term Magnetomotor, 



18. Patent Portable Static Lamp. — A lamp under this name 

 has just been perfected by Mr. Parker, of Argyll-street. Its 

 chief mei;it is, that the oil is raised to the burning height with- 

 out springs, valves, or screws, and in a manner not liable to get 

 out of.repair. To render its principle and construction intelligible 

 the following short account of the ingenious method by which 

 Mr. Parker has effected his object, will probably be sufficient ; 

 in our next Number we shall describe it more accurately with 

 the aid of a plate. 



A cylindrical vessel, open at top, S-j'V inches diameter, and 



