PARAFFIJTE, ETC.] 



UNDULATORY FORCES. LIGHT 



139 



the light to be polarised, and the whole effect was very 

 striking, for the light upon the column was exquisitely 

 beautiful its brightness was magnificently brilliant. 

 The interposition of the red shade then informed us 

 that the light would be changed. When that change, 

 whatever it were, was made, the light sensibly increased ; 

 we then could see the time by the seconds-hand of a 

 small watch ; the usual hand-writing was read ; and the 

 ivy-leaves on the gateway tower were seen at the dis- 

 tance of ninety feet. Persons more than half a mile 

 behind the keep could plainly see the walks around it ; 

 and we all were very much pleased by the striking effect 

 produced by your turning the reflector upwards towards 

 the clouds, which we clearly saw, the light then having 

 the appearance of the tail of a huge comet, the reflector 

 being the nucleus. I think I may state that the breadth 

 of the intensity of the light was at least three-quarters 

 of a mile; and I believe that persons standing on the 

 brick-field (close to Devonport) saw the light reflected to 

 them from a looking-glass which was suspended from the 

 keep. " 



If the electric light is exhibited in a room where there 

 are gas or other lights, the intensity of the former is so 

 great that it actually produces shadows of the flames of 

 the others. At the Polytechnic Institution, the electric 

 light is used for the purpose of illustrating the optical 

 effects of refraction and reflection in a stream of water 

 as seen in Duboscq's fountain. The chromatic effects are 

 produced by means of coloured glass, which is rapidly 

 shifted before the light. 



to the economy of the light, little can be said. 

 Professor Grove stated, that in his experiments with 

 the batt<;ry which gave the light of 1,444 wax candles, 

 the cost was at the rate of about 3s. or 3s. (3d. per hour ; 

 and Mr. Ward, who has devoted attention to this part 

 of the subject, states, that to obtain a given light with 

 100 pairs of Smee, 55 of Daniell, or 34 of Grove, each 

 cell consuming GO grains of zinc per hour, the cost would 

 be about W., 7W. , or Sd. per hour respectively. But 

 we apprehend that this does not include the original 

 cost of the battery, or the charge for attendance. At 

 the Royal Opera House, where the light was exhibited 

 for several nights in a new ballet, it cost the manager 

 2 per night, although the exhibition was not of long 

 duration. In this case a Maynooth battery of seventy- 

 five cells was employed. 



This clearly indicates that the light can never be 

 economically employed as an ordinary illuminating 

 agent : indeed, it is manifest, that as the source of power 

 is really the same as that of other artificial lights 

 namely, the oxydation of a combustible body it resolves 

 it.self into this : whether it is cheaper to burn gas, oil, or 

 tallow, by means of atmospheric oxygen, or to consume 

 zinc by the aid of water and very expensive acids. Of 

 course some allowance must be made for the value of the 

 products in the latter case ; but then, as a set-off to this, 

 we have to consider the expense of constructing tho 

 batteries, and of attending to them. It will, however, 

 be freely admitted, that although it is not an economical 

 light for ordinary purposes, it may be advantageously 

 employed whenever a vast amount of illuminating power 

 if required, and there are facilities for charging the 

 batteries. It might be employed, for example, in light- 

 houses, perhaps also in mines, in theatres, and for 

 public exhibitions of various kinds. It has teen stated 

 that the electric light has been used to illuminate the 

 works of the Napoleon Docks in Paris, where the men 

 are employed night and day in their work. Tho light 

 h.-is been employed there for four months, at a cost of 

 thirty-six francs per night : and as it served for the use 

 of 800 men, the cost was exactly four-and-a-half centimes, 

 or less than a halfpenny, per man. This does not look 

 like a very expensive mode of illumination ; and it is 

 very probable that it may be resorted to in such cases as 

 this witli considerable advantage. Again, it is not alto- 

 gether impracticable to have an electric light in some 

 convenient part of a mine, and, by the aid of reflectors, 

 to throw the light alontj the different galleries, and into 

 *he workings. By this means all danger from explosion 



in those localities where the fire-damp abounds, would 

 be completely obviated. 



Tine Steel Mill of the Miner is the last form of apparatus 

 for the production of artificial light to which we shall 

 allude. Before the introduction of the Davy lamp into 

 the coal-mines of this coxintry, a rude instrument was 

 employed by- the miner for the generation of light in 

 those localities where the fire-damp rendered the atmo- 

 sphere unusually dangerous. It consisted of a small 

 steel wheel, which was made to revolve very fast by 

 means of a small pinion that was turned by hand ; and 

 while the wheel was revolving, a piece of flint was held 

 against it, so as to emit a brilliant shower of sparks. 

 These gave out sufficient light for the miner to work by. 

 It was thought that the heat from this apparatus was 

 less dangerous than that from a candle ; but Dr. Pereira 

 succeeded in firing explosive gas with it, and thus 

 demonstrated to the Parliamentary Committee that it 

 was just as dangerous in a mine as a candle. At the 

 present time the instrument is quite out of use. 



Although the subject of artificial illumination has been 

 fully dealt with in the preceding pages, the following 

 remarks may prove interesting and useful to some of our 

 readers. We have taken each subject separately, and 

 supplementary to what has been already advanced. 



Young's Paraffins Lamps. Mr. James Young, of 

 Bathgate, near Edinburgh, has, for some considerable 

 time past, been engaged in producing an oil for illumi- 

 nating and other purposes, from a shale known as the 

 Torbanehill mineral. With respect to this substance, we 

 may observe, that there is hardly anything in the way 

 of scientific discovery which has proved BO difficult to 

 classify. Nearly every eminent chemist in Europe has 

 been called on to decide as to its nature ; the question 

 being, whether it should be regarded as coal, or as a 

 mineral substance. Owing to the terms of the lease, 

 the lessors reserved their rights to the minerals on tho 

 property ; whilst the lessees object and resist all claim on 

 them, by asserting that the substance from which the oil 

 is obtained does not fall within tliat category. Adver- 

 tisements have been freely distributed in the leading 

 papers by the lessors, since the commencement of this 

 year (18U1), inviting all competent persons to afford 

 their advice and assistance ; and as the means of warfaro 

 are not wanting on either side, and as the prize is of 

 almost fabulous valuo, we may expect to find a most 

 exciting contest before the Court of Session, in Scotland, 

 at the impending trial of the case. The object is to 

 invalidate Mr. Young's title in the question, so far as 

 liis patents are concerned the right to use the material 

 having been compromised by the parties. 



Paraffine itself is so well known as to require no de- 

 scription ; and Mr. Young uses a form of lamp similar to 

 the one already illustrated.* Such are, however, modified 

 as to size, ornament, itc. ; and the paraffine lamp may 

 now be seen in the humblest cottage, and in the residences 

 of our nobility, so popular and general is its DM 



The Fitzmaurice Light. This invention caused a con- 

 siderable sensation amongst naval circles, on account of 

 its brilliancy and portability. For some time its arrange- 

 ments were kept secret ; but it is now stated that it is 

 simply a modification of the lime light, the gases being 

 kept in small reservoirs, into which they are pumped to a 

 high pressure. 



The Lime. Light. This light has lately been partially 

 used for street purposes ; and for the sake of introducing 

 it into popular notice, one side of Westminster-bridge 

 was lighted up with it. A company was formed to carry 

 out its general adoption. We believe, however, that 

 nothing further has been done than what wo have men- 

 tioned ; and until a cheap and ready mode of obtaining 

 oxygen is discovered, it is very unlikely that the lime 

 light will be generally adopted. 



The Electric Light. This subject we shall fully enter 

 into hereafter; but we may just mention, thab Mr. 

 Holmes has, within the last few years, made a con- 

 siderable improvement in obtaining electricity, by 

 feeantf, p, H3j Fig. U7. 



