164 



KNOWLEDGE. 



[July 1, 1899. 



prevails that any electrician who knows his business 

 should be able to tell at once what electricity is. In this 

 connection our esteemed contemporary" Mr. P»wc/j '' did us 

 a great service many years ago, when, representing him- 

 self as having been asked to state what matter was, he 

 replied somewhat in this way, " Matter, matter. Ah ! yes, 

 matter. Well, its — well, no matter." But " Mr. Punch " 

 has many privileges to which the humble tramp toiling 

 on the road of science is in no way entitled. Yet, 

 seriously, it is a serious matter. Only a short while back 

 I was asked, by a man whose intelligence I consider much 

 above the average, " What are X rays ? I want to make 

 some." And there is yet another phase of this trouble. 

 The " man in the street " clings to certain ideas, cherishes 

 them, and absolutely refuses to part with them. For 

 example, it is quite impossible to prevail on the majority 

 to abandon their deep-rooted conviction that the phono- 

 graph is an electrical apparatus. In short, it will be 

 noted that so far as these points alluded to are concerned 

 (and indeed with reference to many others) the electrician 

 requires, and must cultivate, a certain class of experience 

 which is to a great extent unknown in other callings. 



But nothing we can mention in this world is an unmixed 

 blessing. While speaking of experience we must bear in 

 mind that at times it may (under suitable conditions) 

 become a distinct source of error. Eeverting to first 

 principles, under ordinary conditions of life we are justified 

 in saying that where we can neither see nor hear nor feel 

 the presence of anything, there is nothing present. We 

 are so used to the ubiquity of the mixed gas air, that we 

 do not trouble ourselves to mention it, and so we have 

 such an expression as " an empty box." This is hardly 

 to be regarded as contempt due to familiarity, but rather 

 as an error, introduced by too wide an experience. Simi- 

 larly, the student of electrical science has to be brought 

 to realize that even though he cannot see, hear, or feel 

 electricity, yet it may be present, and he has, as already 

 pointed out, to look for its effects rather than for it. 



While it is possible for electricians to learn a great deal 

 from their failures, yet it frequently happens that the next 

 undertaking of a similar nature to that which was not 

 successful is approached with a distinct want of heart, 

 and it will scarcely be too much to state that every elec- 

 trical failure which comes to the knowledge of the pubUc 

 exercises a most pernicious effect upon them. Witness 

 the trouble experienced in order to capitalize the earlier 

 Atlantic cables, and note that the Royal Albert Hall, of 

 which Londoners are justly proud, is not yet electrically 

 lighted. Further, the public having noticed certain 

 electrical failures have adopted the catch words " That 

 shows the difl'erence between theory and practice." For 

 this there are two causes, they mis-apply the experience 

 they have, and overlook the fact that any idea which works 

 out satisfactorily on paper, but not in practice, had some 

 essential point or points omitted in its theoretical con- 

 sideration, or " on paper." 



There exists a most unfortunate tendency to consider 

 parrot, or monkey-like, imitation an exercise of experience, 

 if not of the imitators at least of some constituted authori- 

 ties. Also, there is great and serious liability to error 

 from the fact that statements by such authorities are 

 frequently very badly reported where things electrical have 

 been spoken of. Speaking of imitation, it is almost amusing 

 to observe that municipal bodies are now adopting very 

 frequently a curious precedent with reference to electrical 

 undertakings. Having decided to install the electric light, 

 or to undertake the construction of an electrical tramway, 

 the body in question will depute some two or three of its 

 number to go and inspect the system or systems in use by 



other such bodies. Speaking gently of this practice one 

 is bound to admit that it seems clumsy and expensive. 



When the results achieved by Tesla, Rontgen, and 

 Marconi were first announced the majority of electricians 

 found that to become thoroughly conversant with their 

 full import it was actually necessary to abandon many of 

 their preconceived ideas, and even then, what they had 

 been led to regard as well-founded conclusions, derived 

 from past experience, still formed something of a stumbling 

 block. Similarly, an electrician who has become thoroughly 

 used to direct-current work will, if he suddenly find him- 

 self called to undertake investigations with reference to 

 alternating currents, for some time to come find much of 

 his past experience (though perfectly accurate in so far as 

 it went) a decided nuisance to him, for the time being at 

 least. It might be urged that these latter instances tend 

 to show the danger arising from incomplete experience, 

 rather than the danger of certain experience ; but this 

 contention cannot be allowed, for, returning to one of our 

 previous illustrations, the error which usage permits in 

 the expression " empty box " is not due to the fact that we 

 have no experience in lacuo. 



Perhaps of all the errors into which electricians as a 

 body have ever fallen, solely on account of commercial- 

 electrical teaching or experience, the one most widely 

 spread was that which led them (well within the past ten 

 years) to deride the teaching in schools of " frietional elec- 

 tricity." It used to be said that to teach a boy what would 

 happen when silk, or sealing wax, or glass, was rubbed, 

 was a mere waste of time, because it was not the electricity 

 of commerce. It was pointed out that " frictional elec- 

 tricity " had but two commercial applications, for it was 

 only made use of to de-electrify silk, when in the process 

 of manufacture it became electrified, and hung together, 

 with a tendency to become entangled, and to electrify the 

 ink contained in the telegraphic syphon recorder. When, 

 later on, this latter field for the remunerative use of the 

 despised form of electricity was no more (owing to the 

 introduction of a clockwork tapping apparatus which was 

 found more convenient as a means of making the ink 

 " jump " out of the tube), the electrician's tolerant smile 

 at the " science master " became something painfully like 

 a grin. But all that has been changed by the three men 

 just mentioned (purposely in conjunction, though their 

 work has been independent, and productive of widely 

 different results). Before leaving this point, let me confess 

 that I personally did my best to become one of the 

 broadest grinners at the " science master." All I can say 

 in extenuation is that, having cultivated a certain class of 

 experience, I fell into the pit which I had dug uncon- 

 sciously for myself, and, arrived at the bottom — well, I 

 had good company there. Yet the value of experience 

 must be by no means under-rated. Perhaps the plain 

 statement of fact is best expressed by the assertion that 

 amongst electricians, particularly, it requires great ex- 

 perience to arrive at a just appreciation of the value of 

 experience, and a wide experience to make a proper use of 

 experience. ^_ 



THE TEETH ON THE LABELLA OF THE 

 BLOW FLY. 



By Walter Weschb. 



ONE of the most familiar objects that is mounted as 

 a slide for the microscope, is the proboscis of the 

 Blow Fly (musca voinitoria). Probably the most 

 modest collection of objects contains a slide. It is 

 used every day as a test for low powers, for flatness 

 of field and sharpness of outline, and even familiarity has 



