Ancient Light Questions.

Progress, Volume IV, Issue 2, 1 December 1908, Page 61

Ancient Light Questions.

In disputes as to ancient lights the author advocates the intelligent use of the illuminometer as the only certain way of arriving at an equitable conclusion, and he points out that the experts who give evidence in these cases often betray ignorance of some of the most essential factors. The problems involved in ancient light eases (he says) are really insoluble except by the application of practical photography, but when so solved they are quite simple. The law first requires to know whether a new building has or has not damaged the light of an existing one, to a degree below that generally obtaining in the surrounding districts, and which is, in fact, a nuisance. If that is the case it then requires such damage to be stated in terms which can be translated into monetary damages. Every window is simply a means for obtaining a certain proportion of the sky brightness for interior illumination. "Windows with an horizon more or less obscured are naturally less efficient illuminators, but their efficiency

remains practically constant throughout the wide range of constantly varying sky brightness. If the middle of a room enjoys an illumination of 2c.ft. with a grey sky brightness of 280 c.p. per foot superficial, it will enjoy o.sc.ft. with a grey sky bright-

ness of seventy candles. The use of a Trotter illiirainometer provided with a daylight reducer will fix for any room in a few minutes the ratio between sky brightness and interior illumination, and a comparison

showing this "window efficiency" of rooms alleged to be damaged as compared with that of a number of rooms at the same floor level in the neighbourhood can be easily obtained, and is precisely the evidence required by the Courts.