288 



* KNOWLEDGE ♦ 



[July 1, 1886. 



has given no evidence in favour of the doetiine that all 

 existent forms so descended, any more than it has given 

 evidence in favour of the doctrine that the whole human 

 race was once represent3d by two persons. Many believers 

 in the doctrine of descent consider that when life tirst began 

 on this globe (whether at an epoch or during an era) forms 

 as multitudinous and varied as those now existing made 

 their appearance on the earth. Be this, however, as it may, 

 it Ls certain that, during the enormous periods over which 

 palaeontology ranges, there has not only been no modi6cation 

 from more to less generalised types, but that, as Professor 

 Huxley long since stated, '■ an impartial survey of the po.si- 

 tively ascertained truths of pala;ontoh)gy negatives that 

 doctrine." 



INCOMBUSTIBLE THEATRES. 



By Henry J. Slack. 



T is strange that theatres continue to be built 

 so as practically to insure their being burnt 

 down before they have been in existence many 

 years, whereas it is quite possible, not to say 

 easy, to render such accidents very improbable. 

 It may be conceded that a theatre will be sui-e 

 to have in its stage and property depart- 

 ments a considerable quantity of materials easily ignited, 

 and sure to blaze. Even this ini'jht be pi'evented, but 

 complete prevention would be too troublesome, and perhaps 

 also too expensive. What ought to be done is to ensure 

 that a blazing up of the readily combustible matter should 

 not be able to ignite the main .structure, or any large p.art of 

 it. All the recent theatrical fires have shown that the 

 arrangements, where any exist, intended to secure this object, 

 fail, and so they will do until wiser principles of con- 

 struction are acted upon. The spectators' part of the 

 theatre, the auditorium, with its entrances, stairs, passages, 

 &c., ought not to contain any matter that is inflammab'.e, 

 or easily combustible, even if attacked by a large body of 

 flame arising from gas escape, or fiery outburst on the 

 stage or property part. Brick, or stone and iron, should 

 constitute the framework, and where wood could not be 

 conveniently dispensed with, it should be prepared under 

 hydraulic pressure with tungstate of soda, or some such 

 substance, and covered with an incombustible paint. All 

 hangings and seat-covers .should be impregnated with the 

 tungstate. The seats should be made soft, with steel 

 springs, or stuffed with the fibrous material made out of 

 iron slag, and known as silica cotton. 8o far as possible, 

 the stage properties and appliances should be tireproofed 

 upon these principles. At the worst, what would then happen 

 would be a fire that could not, as now, rage in a few minutes 

 to utterly hopeless proportions. In most cases of theatre 

 destruction the gain of a little time would have enabled 

 the building to be saved. With an auditorium constructed 

 as suggested, its materials could not be quickly raised to 

 anything more than a dull, smouldering state, even if a con- 

 flagration in the stage part wei'e not soon cut off from it 

 by descent of an iron curtain. All floors, except the stage, 

 might be made of iron and cement, and wood entirely 

 banished from the greater part of the buihling. 



The cost of such a construction might bo more than the 

 price of a theatre calculated to perish in less than twenty 

 years of ordinary risk, but it could be insured at a much 

 lower rate, especially if supplied with plenty of pijics con- 

 taining one of the anti-conflagi-ation fluids, which would bo 

 let out as soon as a fire raised plugs of a fusible metal within 

 a few degrees of the boiling-water point. No building 

 can come near the condition denominated fireproof if any 



large portion of it contains so much readily inflammable 

 matter that within a few minutes of ignition it is converted 

 into a fiery furnace with heat enough to twist iron and 

 crack stone. It surely is not essential to a theatre to be in 

 this condition. The property part is, of coiuse, the most 

 dangerous, but even there steel could replace wood for all 

 framework and supports, and, where space is not so valu- 

 able as to prevent it, stores of all kinds should be in a 

 separate building ; if not, divided from the other parts by a 

 party- wall. 



COMPOSITE PORTRAITS. 



HE four accompanying pictures are good 

 illustrations of the method of compcslte 

 portraiture, advocated long since by Mr. 

 Francis Galton. They were taken last year 

 in America, at the suggestion of INIessrs. 

 Brewer &, Pumpelly, and are among the 

 earliest American successes in this method. 

 The object of the method is to portray types, excluding 

 individual peculiarities. Mr. Galton has pointed out that 

 in travelling through a country, peopled by an alien race, 

 the voyager seems to recognise a general similarity among 

 the persons whom he meets, because he is struck by the 

 general characteristics — nOvel to him — of the race; and so 

 gives less attention to peculiarities affecting individuals than 

 he would were he among faces more fiimiliar. In a similar 

 way, the i-esemblance which a stranger finds among the 

 members of the same family is explained. Those who being 

 of that family do not much notice its general type recognise 

 the differences which really exist much more clearly, and 

 wonder that any one can .see resemblance where they see 

 such obvious distinctions. Composite pictures, in like 

 manner, bring out the characteristics which are common to 

 a race or family, and hide those which are exceptional. 



In Science, an American paper, from which the accom- 

 panying pictures were taken, the following particulars of 

 the construction of the pictures are supplied by Mr. 

 Pumpelly : — 



" The individuals entering into these composites were all 

 photographed in the same position. Two points were 

 marked on the ground glass of the camera ; and the instru- 

 ment was moved at each sitting to make the eyes of the 

 sitter exactly coincident with these points. The composites 

 were made by my assistant, Mr. B. T. Putnam, who intro- 

 duced the negatives successfully into an apparatus carefully 

 constructed by himself, and essentially like that designed by 

 3Ir. Galton, where they were photographed by transmitted 

 light. The arrangements of the conditions of light, itc. 

 were such that an aggregate esposui'e of sixty-two seconds 

 would be sufficient to take a good picture. 



" What was wanted, however, was not an impression of one 

 portrait on the plate, but of all the thirty-one ; and to do 

 this required that the aggregate exposure of all the thirty- 

 one should be sixty- two seconds, or only two seconds for 

 each. Now, an exposure of two seconds is, under the 

 adopted conditions, too short to produce a perceptible effect. 

 It results from this, that only those features or lines that 

 are common to all are perfectly given, and that what is 

 common to a small number is only faintly given, while 

 individualities are imperceptible. The greater the physical 

 resemblances among the individuals, the better will be the 

 composites. A composite of a fiimily or of near relatives, 

 ■where there is an underlying sameness of features, gives a 

 very sharp and individual-looking picture. 



" It would be difficult to find thirty-one intelligent men 

 more diverse among themselves as regards facial likeness 



