502 



NA TURB 



[October 21, 1909 



localities. Other types of lamps are the Blanchard, the 

 Petrolite, &c., which are described in detail. 



A special account is also given of petrol air-gas light- 

 ing, thrt^- typical systems, the Machine Gas Syndicate 

 (Cox's svi-tem;, , the .Aerogen, and the National Air Gas, 

 being e.shibited. This system of lighting has attracted 

 great attention recently for the lighting of private houses 

 in districts where gas or electricity are not available. A 

 mixture of a small percentage of petrol vapour with air is 

 generated outside the building, and passed through pipes 

 to the burner in the usual way. 



The method of lighting by alcohol lamps is worth con- 

 sideration in agricultural districts where petroleum may ! 

 not be available, but alcohol is readily manufactured. 

 There are also a number of liquid-gas systems in which 

 gas is stored under pressure in liquid form, and has been 

 effectively used for railway-carriage lighting, &-c. 



Acetylene Lighting. 



Mr. Gaster deals briefly with the historical development 

 of acetylene lighting, and describes the modern form of 

 generator and several types of portable acetylene lamps ; 

 these are frequently used in mines, for motor-cars, &c. 



Acetylene, like petrol-air gas, finds its main apjilication 



The Ulbricht globe photometer, by the aid of which the mean spherical candle-power of a source ca 

 be determined by a single measurement. 



where gas and electricity are not available. A recent 

 development of considerable interest is the method of dis- 

 solving acet\"lene in acetone, which, at a pressure of ten 

 atmospheres, absorbs about 240 times its own volume of 

 acetylene, but liberates it when the pressure is released. 

 Tubes of dissolved acetylene have been widely used for 

 portable lighting, on motor-cars, railway trains, and even 

 in emergencies for interior lighting. Perhaps one of their 

 most successful applications, however, is for the lighting 

 of buoys and beacons in remote localities. 



There arc several types of ingenious valves which are 

 very effective in saving the consumption of acetylene in 

 the above circumstances. For instance, the Dalen solar 

 valve automatically cuts off the main supply of acetvlene 

 in daylight, leaving only the bye-pass burning, and re- 

 kindles it at night. 



General Problems in lUuminaiion. 

 In the last of these four lectures Mr. Gaster discusses 

 the question of illumination in general terms. He again 

 directs attention to the increasing brilliancy of modern 

 illumination, and points out that the eye must have 

 developed mainly in compliance with daylight conditions, 

 NO. 20S6, VOL. Si] 



and therefore we ought not to utilise artificial methods of 

 lighting differing too widely from diffused daylight. The 

 importance of providing for proper access of daylight in 

 the design of buildings, particularly schools, is insisted 

 upon. In this connection, the choice of wall-papers and 

 the scheme of decoration are of considerable importance. 



It is pointed out, too, that the intrinsic brilliancy of 

 illumination has gradually increased of recent years. The 

 effect of gazing directly upon such bright sources is very 

 fatiguing and distressing to the eyes, and the author 

 suggests that the time is now ripe for Governmental re- 

 conmiendations on this point. 



In order to reduce the intrinsic brilliancy of light 

 sources, suitable shades may be employed, and special 

 reference is made to the Holophane diffusitig globes and 

 reflectors, which enable the light to be distributed and con- 

 centrated in any desired direction. 



Some particulars are given of recent progress in photo- 

 metry. The line of development of special consequence 

 has been the introduction of so-called illumination photo- 

 meters, which measure, not the actual intensity of the 

 source, but the actual illumination on the pavements or at 

 the desk at which we read. Sir William Preece so long 

 ago as 18S3 emphasised the value of such measurements^ 

 Another interesting development is the 

 Globe photometer, an example of 

 which is shown in the accompanying 

 illustration. 



Perhaps an exceptionally important 

 development during the last year has 

 been the establishment of the inter- 

 national unit of light between England, 

 France, and the United States, and 

 the recognition of a simple relation 

 connecting this unit with the value in 

 use in Gennany. The success of co- 

 operation in this direction- in this 

 country is felt to be largely due to 

 the fact that representatives of the 

 gas industry and the gas referees 

 wore invited to act with those con- 

 nected with electricity on the com- 

 mission studying this subject. 



Turning next to some practical ex- 

 amples of illumination, the author 

 insists upon the importance of 

 adequate school lighting, quoting 

 many authorities to show that the 

 evesight of school children deteriorates 

 during school life ; he suggests that 

 tests of the children's condition should 

 be accompanied bv the preservation of 

 data relating to the methods of 

 illumination nmnloved in such schools, 

 as this is believed to have a very vital 

 influence on the health of the child. 



In the same way the lighting of 

 factories, hospitals, libraries, &c., 

 should receive very careful study, for 

 good illumination is as much a necessity as the provision of 

 adequate sanitation and good ventilation ; it is hoped that 

 in the future, conditions of illumination, like the matters 

 referred to above, will become the subject of Government 

 inspection and recommendation. In addition, it is pointed 

 out that even from the point of view of expediency 

 employers would do well to pay attention to this matter, 

 as a relatively small expense involved in securing good 

 lighting is more than counterbalanced bv the imorovement 

 in the quality and output of work. In hospitals it is 

 obvious that the lighting should be exceptionally perfect, 

 since people in an invalid condition are specially liable to 

 feel the effect of bad methods of lighting. 



Libraries, again, are frequented by people engaged in 

 strenuous work and taxing their eyes severely : it is there- 

 fore suggested that in this case also no pains should be 

 spared to make the methods of lighting convenient to the 

 workers, and that when great expense is incurred in 

 collecting valuable books and housing them in handsome 

 buildings, the provision for thf necessary illumination 

 bv the aid of which the books alone can be read should 

 not. be crudged. 



A subject on which cooperation between different author!- 



