t M! I. v TORY FORCES. ELECTRICITY. 



[CALORIFIC r.rrfcn. 



Fig. 49. 



appearance; and if n powerful battery be employed, 

 how.- of sparks will sometimes rue from tho metal to 



:l kli '.! ? * J 



Jtfftnmnt 38. I'our some mercury into a wine or 

 other glasa, and inanrt ona of the win* of the battery. 

 Introduce the other wire of the battery, and then with- 

 draw it to a distance of a quarter of an inch from the 

 v surface. A very brilliant flame will be produced, 

 of a bluish-given colour; ami the mercury will l.iini 

 r-iM.llv away, affording dense fumes, which should be 

 carefully avoided. 



litioation of thin experiment ha* been applied by 

 MIU an apparatus, by UH u^ ..f 



which he obtain* a tolerably continuous electric li^ht. 

 Two surfaced of m.-n-nry, or one of platina and mercury, 

 are used; and the fluid nature of the hitter metal 

 permit* of an almost constant distance being kept up 

 between the two terminals of tho Kittery. By tins 

 m^n, one of the great objections to tho electric light 

 it* want of constancy is overcome. 



JBaperimctU 39. Proceed as in the last experiment; 

 but introduce a steel wire, or watch-spring, in place of 

 the copper wire of the battery, anil withdraw it a short 

 distance from the mercury. A splendid oombtutiao 

 will ensue, and the sparks of 

 melted steel will be driven 

 about in all directions, afford- 

 ing one of the most beautiful 

 experiments with which we 

 are acquainted. Great care 

 should be taken in the ex- 

 periment, lost particles of the 

 meltod metal enter the eyes 

 an occurrence which may take 

 place, and wlu'ch might be a 

 source of injury. The an- 

 nexed engraving illustrates 

 the mode of carrying out this 

 beautiful experiment. 



Experiment 40. Another 

 plan of burning steel, is that of holding one of the 

 wires of the battery in contact with a piece of coke, 

 whilst a tile or knife, to which is attached the other 

 wire of the battery, is brought into contact with it, and 

 thru separated from it. The combustion is often so 

 powerful a* speedily to destroy a good-sized file; and 

 the effect, with a large battery, is frequently of the 

 most brilliant description. Tho preceding experiments 

 illustrate what is called the disruptive discharge of 

 the voltaic battery ; and whilst we have selected a 

 few only of the metals, the rest afford very beautiful 

 tenth. 



Some of tho experiments we have named may be 

 easily tried under water, by introducing one of the wires 

 into a yessel full of that liquid, and containing some 

 mercury at the lower part, in which one wire should 

 rest The other wire is to be dipped into the water, 

 and then into the mercury, and to be withdrawn, as in 

 the previous experiments. The discharge will thus take 

 place beneath the liquid, and tho singular appearance of 

 flame undor water will be presented. 



Kfperimtnt 41. Fill a basin with iron or steel filings, 

 and dip one of tho wires of the battery into them. 

 introduce the other wire, and stir it about roughly 

 for some time. Tho filings will gradually become heated, 

 and at last red-hot. It is advisable to try this ex; 

 mont on an iron tray, to prevent any risk of accident, in 

 case the basin may break. Occasionally the filings will 

 become almost fused into a solid mass, owing to the 

 intense heat which is produced. 



i'ltf 42. The heat afforded by the disruptive 

 discharge is very great, as may be shown l>y introducing 

 a piece of platina between the charcoal points of a bat- 

 tery in powerful action, when it will be speedily meltod. 

 The diamond m.iy thus be easily burned, or even evapo- 

 rated away in this manner. 



The foregoing ei|>erimenU will illustrate some of tho 

 moat interesting of tho luminous effects of voltaic elec- 

 tricity. If conducted with a battery of great power, we 



should warn the reader that the intense light produced 

 is very injurious to the eyes. Indeed, the pain H 

 times is intolerable when severe inflammation ensues. 

 Green shades, or spectacles, should always be emp < 

 whilst conducting these experiments. 



THE CALORIFIC FFFECTS OF VOLTAIC 

 KCTUICITV. 



HAVING investigated the luminous effects which may be 

 obtained from tho voltaic battery, wo shall now proceed 

 to describe the heating effects which may be produced 

 from the same source ; and shall presume that a battery, 

 similar to that we have already described,* or one of 

 larger size, will be employed. 



It will be observed, that the thick wires which convey 

 the electricity from the battery, are not easily heated*, 

 except at the points, after they have been in contact. 

 This is because they are sufficiently large to carry the 

 current without affording any considerable resistance to 

 its passage. If, however, these wires are joined together 

 by means of a thin iron wire which is too small to > 

 the current, and which accordingly affords great 

 sistancc to its passage, then a largo amount of heat will 

 be sot free, and the wire will cither be greatly heated, 

 or if the battery be very powerful, the heat will be 

 sufficient to melt even a platina wire. The length < if 

 wire heated by any battery dejMmds on the number of 

 cells ; whilst the thickness of the wire which may be 

 melted, depends on tho size of the plates. 



Different metallic wires, of the same thickness, vary 

 in their power of carrying a voltaic current. Copper, as 

 tho best conductor, in the most difficult to melt ; and 

 iron or platina, which are much inferior in their con- 

 ducting power, are very readily heated by tl 

 current, and hence are most suitable for illustrating 



the.se etl'eets. 



The relative conducting power of wires of different 

 metals, or of different thicknesses, may be conveniently 

 illustrated by making a chain of them. Thus, a chain 

 of silver or copper wire, with links of iron wire, will, 

 when made to form part of the conducting course of a 

 powerful battery, present tho appearance of an alterna- 

 tion of cold and red-hot wires. Or the thick wires may 

 be nailed to the edge of a table, and eauh joined by 

 means of finer wire, when tho latter, on conveying the 

 current, will be in- 

 stantly melted. A 

 plan of arranging 

 this is illustrated f 

 in the annexed on- ( 

 graving ; and the 

 effect, if properly managed, is both instructive and 

 pleasing. The heat thus generated may be made to boil 

 water. The fine wire should be coiled into a screw-like 

 form ; and after being attached to the largo conducting 



Fig. so. 



MM 



Fig. II. 



wires of the battery, i; 

 be introduced into a glassful 

 of water. After a short 

 time, the liquid will com- 

 mence to boil, and will soon 

 be evaporated off. The best 

 mode of carrying out the 

 experiment is illustrated in 

 the annexed engraving. 



The elec- 

 tricity of a powerful battery 

 may be conveyed to any dis- 

 tance by moans of properly 

 insulated wires ; and for this 

 purpose, gutta-percha answers 

 admirably. The heating 

 powers of tho voltaic bat- 

 tery have thus been applied 

 for blasting, military, engineering, and numerous other 

 purposes ; and we shall suggest an exj>oriment which 

 will illustrate the plans usually adopted in applying 

 electricity in this manner. 



See mtr, p. 188. 



