880 KEPORT— 1892. 



],330 mm. focal distance, and a height of 5 feet. This lens, which was named 

 ' hyper-radiant,' was tried at the South Foreland against other lenses, and with a 

 large ten-ring gas burner it was found to give a light from one and a half to twice 

 as intense as the ordinary lenses which were pitted against it with the same large 

 burners in their foci, thus proving conclusively that to get the power out of large 

 burners it was imperatively necessary to increase the diameter of the apparatus. 

 In 1883 Messrs. Stevenson got an otl'er from Messrs. Barbier for a lens of 1,840 mm. 

 Jocal distance. 



All refracting lenses from the day of Alan Stevenson were cylindrical for fixed 

 lights, and plano-convex for revolving lights, and no alteration of any moment has 

 been made in the mode of their construction until 1886, when, instead of making 

 the lenses cylindrical or plano-convex, I proposed to give them a spherical form — 

 that is to say, circular not only in the horizontal but also in the vertical section. 

 This design was carried into practice in the apparatus for one of the Fair Isle 

 lighthouses. The introduction of the spherical refractor has made practicable the 

 construction of very much larger and, consequently, more powerful apparatus, and 

 occupyins: much less space both in the daylight size and diameter of lantern. It 

 has rendered practicable the qiiadrilateral arrangement with hyper-radiant lenses 

 which have already been erected at Fair Isle, the lenses being cut so as to give two 

 •flashes from each side of the quadrilateral. An experimental one, made for Mr. 

 AVigham, is to be tried in Ireland. It is 2 m. focal distance, and the spherical 

 refractor is 7 ft. 6 in. in diameter, and will give one flash from each side of the 

 quadrilateral. The vspherical refractor should not be carried too lar above the focal 

 plane, and equiangular prisms should then be employed. 



4. Smoke-consuming Apparatus. By A. R. Senxett. 



5. A System of Purifying the SnioJcefrom Domestic and other Fires. 

 By Colonel E. Duliek. 



This process consists in mixing the smoke as it leaves the flue with a small 

 quantity of steam, generated in a boiler forming part of the kitchen range. 



The mixed steam and smoke pass into an open chamber, the top part of 

 which is provided with a number of pipes, placed in the direction of the prevailing 

 wind, through which the air passes and helps to cool the gases. At the extreme 

 top of this chamber, just before passing into the atmosphere, the gases are met by 

 a very fine shower of water issuing from minute holes in a pipe. 



The result of this treatment is a very thorough washing of the smoke, and the 

 almost complete removal of all solid matters (soot and dust) and a large proportion 

 of the sulphurous acid always present in coal smoke. The removal of the soot and 

 dust is so perfect that a piece of wet cotton held in the issuing gases remains 

 perfectly white even after a lengthened exposure. 



The amount of steam required is small, and may be neglected in an estimate of 

 the cost of working the process, as it is generated by means of heat which would 

 not otherwise be available for any useful purpose. The only item of cost to 

 consider is that of water. The amount used in the apparatus at Sloane Gardens is 

 found to be about ten gallons per hour ; this includes the condensed water from the 

 steam. 



This apparatus treats the smoke from a large kitchen range burning about 

 20 lb. of coal per hour, but it is capable of treating the smoke from several such 

 tires. It is important to notice that the draught is not sensibly impaired by the 

 apparatus, any slight retarding of the flow of the gases being more than com- 

 pensated by the action of the jet of steam. 



The results of a number of experiments with the apparatus at atmospheric 

 temperatures varying from 92° Fahr. (33°-3 C.) in the shade (part of the time the 

 apparatus was exposed to direct sunshine) to 50° Fahr. (10° C.) showed that 



