24 



KNOWLEDGE * 



[Not. 1, 1885. 



On the robes of the Great Spirit, 

 As lie passe; through the twilight, 

 Walks in silence through the heavens ! " 



Then lao'oo, the story-teller, relates how Osseo, the 

 son of the wandering star of Evening, was beloved by 

 Oweenee, the "silent, dreamy maiden," who refused "all 

 her young and handsome suitors," and married — 



" Old Osseo, poor and ugly. 

 Broken with age and weak with coughing. 

 Always coughing like a squirrel. 

 Ah, but beautiful within him 

 \Vas the spirit of Osseo, 

 From the Evening Star descended." 



All the heavenly bodies, indeed, were suppcsed to be 

 human beings or spirits by the North American Indi ms. 

 The ghost theory was very obviously held among them, 

 not the mere Fetish worship imagined by some modern 

 writers. 



ELECTRICITY AT HOME, 



By W. Slingo. 



ELECTRIC MACHINES. 



PECULIAR charm attaches to elec- 

 tricity, I think, as a source of interest 

 and entertainment, and this apart alto- 

 gether from the gratification it affords to 

 man J' thousands as the basis of their daily 

 calling. That this has long been the case 

 is evidenced by what we read of the many 

 devotees to the study of the science during the past two 

 or three centuries. There is, however, some danger, in 

 these days of dynamos and telephones, that what Tyndall 

 has aptly called the " older electricity " will be to some 

 extent lost sight of, or at least regarded with less respect 

 than is merited. This is due, in a measure, to the fact 

 that the study of electricity is bald in the extreme if 

 unaccompanied by experiments, while the cost of per- 

 forming such experiments efficiently is, as a rule, a 

 heavy item. I should be one of the last to say that 

 the makers of good scientific apparatus ask too much 

 for their wares, for the workmanship put into the in- 

 struments is worthy of good remuneration ; but when 

 one cannot run to the expense of the more costly appa- 

 ratus, it is false economy to purchase inferior goods. 

 The expense of a first-class article is generally mside 

 heavy by the introduction of little details and eliibova- 

 tions, requiring a deal of labour and attention, and yet 

 not essential to the more general application of the instru- 

 ment, whatever it may be. The working man, more- 

 over, has a tendencj- to work according to his "stuff," 

 i.e., if he is using common deal where ordinarily ma- 

 hogany or walnut is employed, he puts in propor- 

 tionately jioorer work and the instrument consequentlj' 

 acts but indifferently. Cheap apparatus is therefore as 

 often as not a delusion. Nevertheless, I think it within 

 the power of anj-one of average ability to provide him- 

 self with apparatus of a highly efficient character at a 

 comparatively trifling cost. Such apparatus, too, will 

 afford fnr more pleasure than if it were purchased, while 

 the most inexjjerienced can, by beginning with simple 

 instruments and producing subsequently more and more 

 intricate ones, gain that experience and knowledge of 

 apparatus which is essential to the real enjoyment of 

 Science and its teachings. 



The instrument which, for simplicity of construction, 

 and, at the same time, gener.U utility as a sour.^e of 

 experiment, excels vAl other.s is the electric machine. 



With a well-made machine, even if of the smallest dimen- 

 sions, experiments of an almost endless variety can be 

 performed, while the brilliancy of many of them imparts 

 an interest wliich for a long time has carried all before it. 

 Fig. 1 illu.strates a somewhat elaborate form of that 

 type of electric machine known as the "cylinder," in 

 which a glass cylinder is caused to revolve between a 

 piece of silk on the one side and a metallically-connected 

 row of pin-points on the other side, the points being 

 connected to a metallic cylinder by means of metal rods, 

 tubes, lie. From such a machine copious discharges of 

 electricity may be readily obtained. Let us, however, 

 consider a simpler form of the instrument, and one which 

 can be well made at a co.st not exceeding five shillings. 

 The first thing to do is to get a cylinder. This may 

 consist of a glass bottle or jar such as confectioners use, 

 or it may even be an ordinary plum-jar. It is essential, 

 however, that the surface should be smooth, and free 

 from any irregularities ; the sides, too, should be parallel 

 — that is to say, a vertical section should yield two 

 parallel straight lines. Some little care also should be 

 taken in selecting the best or most suitable quality of 

 glass. Some kinds of glass are much inferior to others 

 as insulators. The best sort for our purpose is that 





Fig. 1. 



greenish-looking glass employed for windows or common 

 bottles. Some trouble is likely to be experienced in jiro- 

 curing a bottle answering to these requirements, and after 

 all it will be found in many cases preferable to purchase a 

 regular cylinder, more especially as the cost is reasonably 

 small, and there is no fear that it will prove too poor an 

 insulator for the purpose. A cylinder four inches in 

 diameter and seven inches long may be purchased for 

 two shillings or half-a-crown. The shape will be found 

 similar to that illustrated in Fig. 2, A B being apertures 

 through which the axis is to pass. Presuming these aper- 

 tures to be three quarters of an inch in diameter, the axis 

 or spindle may consist of a rod of beech or some other 

 hard wood of about the same diameter. Failing anything 

 better, however, a piece of a stout walking-stick will 

 answer the ptirpose, or even a broom-handle will do, if 

 one can be procured small enough in diameter. Before 

 the cylinder is fixed on to the spindle the base and 

 supports should be put together so that the cylinder may 

 be properly balanced and a handle fitted. The handle 

 may give a little trottblo to make, but it is not a verj- 

 serious matter. It ra.ay be of wood or metal, accord- 

 ing to convenience. If it is to be of wood, cut a strip 

 half an inch thick, an inch or so wide, and five inches 



