--------------------------+-------+--------+---------------------+-------- Kind of Burner. |Cubic |Pressure| Illuminating Power. | |Feet of| in +----------+----------+Increase |Gas |Inches. |Without |With | per |per | |Perfecter.|Perfecter.| Cent. |Hour. | | | | --------------------------+-------+--------+----------+----------+-------- Leoni's fishtail, No. 2 . | 3 | 0·84 | 1·3 | 4·1 | 215 Leoni's fishtail, No. 3 . | {3 | 0·46 | 2·4 | 4·6 | 91 | {4 | 0·70 | 2·8 | 6·5 | 132 | {3 | 0·31 | 3·4 | 5·0 | 47 Leoni's fishtail, No. 4 . | {4 | 0·47 | 4·5 | 7·6 | 68 | {5 | 0·71 | 5·0 | 9·2 | 84 | {4 | 0·42 | 5·3 | 6·9 | 30 Leoni's fishtail, No. 5 . | {5 | 0·60 | 6·1 | 8·3 | 36 | {6 | 0·81 | 7·1 | 10·0 | 40[5] Leoni's fishtail, No. 6 . | {4 | 0·31 | 6·2 | 8·0 | 29[6] | {5 | 0·46 | 8·0 | 10·4 | 30[7] --------------------------+-------+--------+----------+----------+-------- [5] Flame flickers. [6] Do. [7] Flame flickers a great deal. Burners were also made with the metal plate forming part of the burner head; and, instead of being of platinum, it was sometimes formed of thin steel, or other commoner metal. Where platinum was used, some advantage probably accrued from its becoming incandescent; but, of course, any benefit arising from this source was not obtained when steel was employed. The remarks which have been made respecting the limited applicability of the double-flame burner will apply, with equal force, to the apparatus under notice. Although it effected an undoubted improvement when applied to burners ill adapted to the pressure at which the gas was supplied, equally good results could be obtained without its aid, when a burner was employed suited to the quality and pressure of the gas supplied. [Sidenote: Leoni's flat-flame burners.]