CHEMISTRY. 227 



and other places of business, where doors are constantly open, and there are 

 other means of ventilation, it is not so. There a great quantity of light is 

 necessary, and, as frequently happens, the number and arrangement of the 

 gas-burners are intended to attract attention even more than the goods dis- 

 played for sale. In the quietness of the family this must be avoided. For 

 special purposes, it may be desirable to have the means of brilliantly lighting 

 up particular apartments ; but on ordinary occasions, gas should be used 

 solely with reference to comfort and utility. 



It is sometimes said that gas light is injurious to the eyes. During twenty 

 years of careful observation and inquiry, no instance of the kind has ever 

 come to my knowledge. A powerful light imprudently used, or improperly 

 directed, might be expected to be hurtful ; but in that case light from oil, 

 tallow, was, or turpentine, would be equally objectionable as that from gas. 

 To say that a good light, in the sense in which the term is here employed, is 

 injurious, and that an indifferent or bad one is not so, is about as reason- 

 able as to affirm that the light of the moon is more useful than that of the 

 sun, or that it is easier and more congenial to the feelings to read, or write, or 

 work by fire light, than by that from candles. 



The eyes are more distressed, and sight more impaired, by a few days 

 .of over-straining hi the dimness of candle light, than by years of closer 

 application in the light from a properly regulated gas-burner. A good gas 

 light, producing as nearly as possible the same effects as diffused sun light, 

 placed at a proper distance from, and above, the eyes, is not injurious ; but, on 

 the contrary, exceedingly agreeable and eminently preservative. The direction 

 in which artificial light falls upon the eyes has not received sufficient attention. 

 Table lamps and candles are, hi most instances, too low ; that is, the light is 

 too near the plane of the axis of the eye to be comfortable, or to produce the 

 best illuminating effects. The natural, and, therefore, the most appropriate 

 position for the light, is at a convenient distance above the eye ; the angular 

 direction being, of course, dependent on the height and dimensions of the 

 room. In this respect, gas has an advantage over other modes of lighting ; 

 the situation as well as the quantity of the light, being deterrm'nable with the 

 greatest accuracy. 



An uncomfortable degree of heat is sometimes complained of as one of the 

 results of lighting a room with gas. By a little forethought, and a few simple 

 contrivances, this might be prevented. Let it be remembered that the 

 quantity of heat emitted by lamps, candles, and gas lights is, in practice, very 

 nearly in proportion to the quantity of light obtained. It matters not, there- 

 fore, what means are employed or materials used in procuring light ; for, if a 

 certain quantity be considered necessary, and there be-more at one time than 

 another, or by using gas instead of candles the quantity be permanently 

 increased, the heat diffused throughout the apartment must necessarily be 

 increased in the same proportion. 



It must also be understood, that the products of combustion are precisely 

 the same in their chemical constitution, whether the light-giving material be 

 wax, tallow, oil, or gas. If gas be well purified, it not only yields a more 

 brilliant light from a flame of the same dimensions, but its combustion is more 



