86 YEAR-BOOK OF FACTS. 



fabric, or other suitable material, and the peat is placed between 

 shelves, and submitted to hydraulic or other pressure. The water 

 is entirely forced out and the peat solidified ; and drying is effected 

 either by exposure to the atmosphere or in a room heated artificially, 

 or by any other process. They are then put again between the 

 plates of a hydraulic or other press, and extreme pressure put on 

 them. If the product of this invention be required for use for 

 inside work in building, such as partitions, linings, inside roofing, 

 or for other work, as a non-conducting substance, they do not require 

 other further preparation than shaping provided they are not to be 

 exposed to wet. But the slabs or pieces used for roofing (instead of 

 slates, tiles, or other things of that nature) they prepare to resist the 

 wet or action of the atmosphere by steeping them in, or saturating 

 or coating them with, some fitting material to resist wet, such, we 

 presume, as pitch. — Builder. 



ELECTRIC ILLUMINATION FOR LIGHTHOUSES. BY PROFESSOR FARADAY. 



Tin: use of light to guide the mariner as be approaches land, or 

 passes through intricate channels, h;;s, with the advance of society 

 and its ever-increasing interests, caused such a necessity for means 

 more and more perfect, as to tax to the utmost the powers both of 

 the philosopher and the practical man, in the development of the 

 principles concerned, and their efficient application. Formerly the 

 means were simple enough; and if the light of a lantern or torch 

 was not sufficient to point out a position, a fire had to be made in 

 their place. As the system became developed, it soon appeared that 

 power could be obtained not merely by increasing the light but by 

 directing the issuing rays : and this was in many cases a more 

 powerful and useful means than enlarging the combustion ; leading 

 to the diminution of the volume of the former, with, at the same 

 time, an increase in its intensity. Direction was obtained, either by 

 the use of lenses dependent altogether upon refraction, or of reflectors 

 dependent upon metallic reflexion : and some ancient specimens of 

 both were shown. In modern times the principle of total reflexion 

 has also been employed, which involves the use of glass, and depends 

 both upon refraction and reflexion. In all these appliances much 

 light is lost. If metal be used for reflexion, a certain proportion is 

 absorbed by the face of the metal ; if glass be need for refraction, 

 light is lost at all the surfaces where the ray passes between the air 

 and the glass ; and also in some degree by absorption in the body of 

 the glass itself. There is, of course, no power of actually increasing the 

 whole amount of light, by any optical arrangement associated with it. 



The light which issues forth into have a certain amoont 



of divergence. The divergence in the rertacal direction must be 

 'i to cover the sea from the horison to within a certain mo- 

 derate distance from th( thai all ships within that distance 

 may have a view of their lominons guide. If it have less, i 

 escape observation where i( ought to be seen ; if it have more, 



• Tli'' ation .'ft; r.-iu Britain, ;<t 



the weekly evening meeting, Friday, Uaroh 9, lstK>. 



