92 ANNUAL OF SCIENTIFIC DISCOVERY. 



proximity of a sino^le luminary. If brackets are to be employed, 

 let there be at least two in a room, and these ilisposed vis-a-visy or 

 as nearl}'' so as possible. 



liejlcdors. — The value of reflectors is not appreciated as it 

 should be, and the reason is principally because few pe()})le, even 

 those whose business is to make ai)paratus for artificial light and 

 attend to the introduction of gas-fixtures, etc., arc sulliciently ac- 

 quainted witii the laws that govern reflected light, and when so, 

 they fail in the mechanical ability to properly arrange reflectors 

 so as to obtain the proper efl"ect. lleflectors should be made of a 

 material that will not tarnish by the action of the atmosphere or 

 the temperature they may be exposed to. A very slight lilm of 

 dust, moisture, or smoke on a reflector will almost entirely de- 

 stroy its value as a reflector. The sm'face of the reflector should 

 be perfectly smooth, and free from scratches and aljrasions. 

 Hence it is apparent that metallic reflectors are not tlie best in 

 that respect. 



Glass reflectors are superior, inasmuch as they do not become 

 tarnished, abraided, scratched, but their action is impaired if the 

 glass is too thick, owing to the absorption of light. The late 

 American invention of a mica reflector is advantageous on that 

 account, because the plates or lamina are very thin. It has also 

 the advantage of not being fragile or liable to fracture. 



Reflectors are better placed overhead. A reflector which 

 throws the light in a horizontal direction, unless neutralized l)y 

 another oi)posite, will be very disagreeable, owing to the (hiz- 

 zling glare. As a rule, reflectors should be so placed tiiat the 

 reflective rays shall never reach the e3'e in a straight line. Tiiis 

 will avoid the evil effects of glare. As a rule, all the direct rays 

 of a lamj) or burner thrown upward may be thrown downward 

 by reflectors, producing a great economy of light, and an eflec- 

 tiveness of illumination very pleasant and satisfactory. 



HEATING BUILDINGS BY GAS. 



In the United States this art has lately acquired a new impulse, 

 owing to the late discoveries and improvements in the art of 

 manufacturing hydrogen and oxide of carbon gases, at a very 

 trifling cost, compared to the cost of ordinary coal gas.. These 

 gases are especially adapted to heating purposes instead of solid 

 fuel and for use in gas engines as a substitute for steam-power, 

 and also for illuminating purposes when carburetted or charged 

 with vajiors of hydro-carbons. 



The iiydrogen and oxide of carbon gases are produced by the 

 American process, under the GwNnne-IIarris patent, which consists 

 in decomposing superheated steam, by means of incandescent 

 anthracite coal, in a peculiar manner, and in a simple yet novel 

 apparatus. 



Great improvements have also been made in the stoves and 

 other apparatuses for heating and cooking, which overcome 



