The London, Edinburgh and Dublin philosophical magazine and journal of science . gral can be expressed interms of the sine and cosine integrals, the values of whichhave been calculated by Mr. Grlaisher, whence numerical-values of the magnetic forces might be found. If we neglect powers of c higher than the fifth, the mag-netic forces in the , z, and p directions will be found to berespectively equal to /.« xde-2Kh ( XV , 5\V\ mB4*C*\7e-*>*dk mKJ0 R2X2 + a>2V~ 4 +T927^+ ~64~J0 WxF+%?; X3e-2A* / a X2c4s \6e~2khd\R2X2 + 9o>2* f« X26-2x/, / xv 5XV5\,^ 3ma>2c5r [ 145 ] XVII. On an Elect
The London, Edinburgh and Dublin philosophical magazine and journal of science . gral can be expressed interms of the sine and cosine integrals, the values of whichhave been calculated by Mr. Grlaisher, whence numerical-values of the magnetic forces might be found. If we neglect powers of c higher than the fifth, the mag-netic forces in the , z, and p directions will be found to berespectively equal to /.« xde-2Kh ( XV , 5\V\ mB4*C*\7e-*>*dk mKJ0 R2X2 + a>2V~ 4 +T927^+ ~64~J0 WxF+%?; X3e-2A* / a X2c4s \6e~2khd\R2X2 + 9o>2* f« X26-2x/, / xv 5XV5\,^ 3ma>2c5r [ 145 ] XVII. On an Electric-light Fire-damp Walter Emmott and William Ackroyd. * THE Royal Commission on Accidents in Mines point out,in their recently issued Report, a serious objection tothe use of the electric light in mines, notwithstanding itsmany other great advantages, in that the light of an incan-descent lamp being produced within a vacuum cannot admitof any device for the indication of fire-damp such as isemployed in the Davy for example. This difficulty was Fig. experienced by one of us in the course of an installation ofthe electric light in the Lofthouse pit, Wyke, Yorks, in thesummer of 1885 ; and we have since made a series of experi-ments with the object of devising a method of making theelectric light an indicator of fire-damp. The apparatusplaced before the Physical Society is the outcome of ourwork. It consists of two incandescent lamps, one withwhite glass and the other with red, and other necessaryadjuncts, such that in an ordinary atmosphere the whiteincandescent lamp alone shines, but in fire-damp the whitelamp goes out and the red one begins to emit its is effected as follows :—A porous pot of unglazed hard-baked porcelain is joined by air-tight connections to a tubea portion of which is represented by TT1, fig. 2. This tube isof such an internal diameter that it will readily admit ofbeing sealed with a small quantity of mercury, H<7. Aplatinu
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
