378 Prof. Bischof on the Employment of the Safety-Lamp 



cord giving 1 off unsjmmctrical nerves, and terminating in a ring 

 which surrounds the pharynx ; // the two genital hooks with their 

 muscles, one of which is common to both, and approximates their 

 upper extremities. Fig. 3. The nervous circle, part of the cord, 

 and the extremity of the latter magnified. Fig. 4. A section of a 

 part of the muscular parietes of the body, and of the sheath of one 

 of the genital hooks, to shew that the latter is a tegumentary or- 

 gan developed in a follicle, and provided with a muscular appa- 

 ratus as in similar organs among the Annelida. Fig. 5. A por- 

 tion of one of the respiratory sacs, magnified to shew the ciliated 

 funnel-shaped processes in the state of erection. Fig. 6. A por- 

 tion of one of the respiratory sacs laid open, to shew the ciliated 

 projections on its internal surface. Each of these corresponds to 

 one of the fnunel-shaped processes on the external surface. Figs. 7, 

 8, D. Diagrams to illustrate the mode in which the sea-water may 

 be supposed to pass through the ciliated organs of the respiratory 

 sacs, into and out of the abdominal cavity. Fig. 7. The organ 

 erected, and the passage free. Fig. 8. The organ half retracted. 

 Fig. 9. The organ wholly retracted, the muscular fibres contracted 

 over it, the passage closed, and the ciliated projection formed on 

 the internal surface of the sac. Fig. 10. Male organs in season. 

 Fig. 11. Spermatozoa. Fig. 12. Female organs in season. Fig. 

 13. Eggs magnified, shewing the cells in their interior. 



On the Employment of the Safety-Lamp in the Coal-Mines of 

 Germany. By Professor Gustav Bischof, of Bonn. (Com- 

 municated by the Author*)* 



Three years ago the Prussian government charged me with 

 the examination of the means of preventing the dreadful ac- 

 cidents in coal-mines, occasioned by explosions of fire -damp. 

 For this reason I have visited many coal-mines in the neigh- 

 bourhood of Saaroruc/cen, TFellesweiler, Aix-la-Chapelle, and 

 in the Principality of Sehaumbery. I have examined into all 

 the circumstances concerning the exhalations of fire-damp, 

 and collected this inflammable gas issuing from blowers in 

 three coal-mines, for the purpose of analyzing it.t Supported 



* Read before the Wcrnerian Natural History Society, January 9. 1841. 



t Our readers are referred to Professor Bischof 's Physical and. Chemical 

 Examination of Fire-Damp, published in this Journal, Vol. xxix. p. 309, 

 and last Number, p. 127. — Edit. 



