PJn/sical and Chemical Papvn^. 11 



their expense of operation, only installed at alternate corners. 

 This means that if there are many trees, the walks especially 

 are very poorly lighted midway in the block. These lamps 

 consume about 450 watts, and are generally rated as 800 to 

 1000 candlepower. For the same number of watts of electrical 

 power used we might install seven or eight 80 c. p. nitrogen- 

 filled lamps, thus making from three to four lights per block ; or 

 if they were distributed along the cross streets as well, one 

 at each intersection and one at the middle of each block. This 

 would give a uniform illumination of sufficient intensity for 

 the smaller city or town where crime prevention is not the 

 main consideration. The cost of maintenance of these lamps 

 averages about $10 per year each, while the arc lamps average 

 $75 per year. These are the prices for both electricity and 

 lamp maintenance. Thus it will be seen that the seven or 

 eight distributed units do not cost more than the one arc lamp. 

 Many cities are tied to the use of arcs for ten to fifteen years 

 yet, on account of the customary twenty-year franchises which 

 are given for the service. There is an enormous amount of 

 money invested in the thousands of arc lamps now installed, 

 and the change to the distributed series tungsten lamps is 

 generally made only at the expiration of franchises. 



Besides these reasons for the illumination of our streets 

 and alleys, there is the problem of rendering certain streets 

 attractive, especially the main business streets. The problem 

 of eflFicient and economical street lighting is of great impor- 

 tance to those actively interested in improving the appearance 

 of any city. The progressive merchant is fully aware of the 

 value of artistic lighting and of its effect on the volume of 

 trade, and it has be^n demonstrated repeatedly that many 

 advantages are gained by the city having a distinctive decora- 

 tive street illumination system. 



Generally speaking, the value of property on a business 

 street is directly proportionate to the number of people who 

 make use of the street as a thoroughfare. A corner lot on the 

 main business street is worth more than a lot in the latest 

 addition to the city, simply and solely because a greater num- 

 ber of people pass that corner every day. It not infrequently 

 happens that opposite sides of a street on the same block have 

 considerably different values, due to the same cause. Any- 

 thing which adds to the traffic of the street must, therefore, 



