■H8 



KNOWLEDGE • 



[March 24, 1882. 



portion. A amall circular platinum washor is placed on 

 one face of oixch ciid, tlii' hookoil cud of tho pliitinuin 

 wire on tlio otlmr, niid a Kiimll l)olt(!) ])aSHCH throuj;li the 

 wholf. Hiiial! nuts screwed on to tlie liolt clump tlie three 

 parts, and so ensure tin- oonncction. 



Tlio Britisli Lamp (Fig. 5) is perhaps the most recently 

 oftered to the public. It consists of a glass globe, 2i 

 inches in diameter, continued by a comparatively long 

 glass tube. The filament is made from cocoa-nut fibre, 

 and is attached at A and B by means of small carbon 



tubes to two short platinum wires, AC and BD. Two 

 other platinum wires, Kl<' and GH, are fused into the 

 lower part of tlie glas.s tvilie, FC and C!II being lengths of 

 copper wire connecting; tli<' platinum.?. Externally, copper 

 wires connect the platinum to the wires from the machine. 



It will doubtleiis l>e noticed that the Bimilarity between 

 the various lamps is, at least in regard to the principles 

 involved, very great. The slight variations or difTen-nceg 

 may lie classed under two heads — viz. (1), the substances 

 from which the filamentR are made, and (2) the methods of 

 connecting the filaments to the external circuit Platinum, 

 so far as is at present known, is the oidy substance avail 

 able for passing throinjh the glass, being the only metal 

 which will fuze into that substance — that is to say, it is 

 the only metal which expands and contracts at the same 

 rate as glass on an increase or decrease of tempera- 

 ture. Its use is, therefore, inevitable. Swan, Edison, 

 and Maxim take their platinums from the filament to the 

 outside of the bulb. Lane-Fox, however, connects the 

 interior to the exterior by means of mercury — a de\-ice 

 which appears useless, for equally good contact could be 

 made by attaching the copper to the platinum. The copper 

 wires inside the British lamp are evidently used on the 

 score of economy, platinum costing alwut ^.os. to 308. per 

 ounce. Whether it is true economy or not, remains to l<e 

 proved. We, however, fail to see why this form of lamp 

 should be valued at lOs., while the Swan can l>e bought 

 for .'^s. 



Great efforts have been made by the difierent exhibitors 

 to secure the public favour, and in some cases these efforts 

 have been successful ; but there are times when we detect 

 traces of a want eitlier of ordinary energj- or of practical 

 knowledge, and it is to the absence of such shortcomings 

 that we must look for an explanation of much of the 

 favour with which Mr. Edison's exhibits are received. 

 Although he has a large staff in London, most of them are 

 Europeans, and are, therefore, not open to the charge 

 some people seem disposed to hurl at them, as accounting 

 for their diligence and enthusiastic loyalty to their employer, 

 \\z., that of being Americans. It would be somewhat 

 invidious to draw any distinction, or to refer to any par- 

 ticular instance of inexperience, but we may mention 

 one which came under our notice some years since. 

 Shortly after the transfer of the telegraphs to the Govern- 

 ment, a number of men were sent to construct a line of 

 telegraph in a woody district not a thousand miles from 

 London. They did their work during the winter months, 

 and followed out to the letter instructions to keep the line 

 as clear of the road as possible. They did their work too 

 well, for when the spring and summer came, and covered the 

 trees with shoots and leaves, the wires were enveloped 

 and lost sight of, and as a consequence the slightest shower 

 of rain rendered them useless. The result of this want of 

 experience was that the line had to be taken down and 

 reconstructed. Electric lighting, however, is a young 

 industry, and some time must elapse before all its votaries 

 acquire their necessary information 



There are other points of great interest in connection 

 with incandescent lighting, which, however, we cannot 

 refer to now, but will avail ourselves of the opportunity 

 in our next notice. 



THE GREAT PYRAMID. 



By the Editor. 



rr^HUS far all has been tolerably plain sailing. Of the 

 X. astronomical use and purpose (not quite the same 

 thing, be it noticed) of the Great Gallery, there can be small 

 room for doubt, when we find (1) every feature in all the 

 passages and in the Great Gallery correspond with the re- 

 (luinnients of the theory, and (2) many features explicable 

 in no other way. 



