influence, the retard of each day's Lava-stream being found to be nearly identical 

 in character with that of a tide. Such is the precision of the instruments of the 

 observatory, which have been used during this eruption, that a person, even 

 with the windows closed, and without seeing Vesuvius at all, can tell with 

 accuracy what are the conditions of the eniption. The observations were com- 

 menced during the long-continued eruption in the year 1855 : at that time a 

 diurnal period was marked by Hamilton, who from his limited number of 

 observations deduced the fact of the recurrences being at fixed hours. This has 

 now been so completely confirmed, that nothing is wanting, but a [rood path, to 

 enable visitors to know the exact hour at which they should be near the summit, 

 without any risk from projectiles or the burning Lava. So that the man of science 

 may say of a burning moimtain even in the whirlwind and fury of its passion, 

 " Though this be madness, yet there's method in It." 



Indeed one could hardly have, in present state of physical knowledge, a more 

 BtriMng proof of the prevalence of law than that afforded by this discovery. 



While on the subject of the destructive powers of Nature, I cannot help 

 referring to one frequent cause of loss of life, of which a notable instance 

 occurred in the explosion at the Oaks Colliery. It is probably known to many 

 of my hearers, that with that fearful catastrophe ended— only for a time I hope 

 — an experiment hardly inferior in importance to any that could be entertained 

 in a coal-mining country. I aUude to the project of applying that terrible 

 enemy the Fire-damp (as it is called) of coal mines to the purpose of their own 

 illumination. The problem remained— if I cannot say a successful, still a 

 practicable one— from the year 1862 down to the time of the explosion— a 

 period of four years — during which sixty burners were acting most satisfactorily 

 day and night. The accident, however terrible in extent, should not be allowed 

 to discourage a project in itself so interesting to humanity as well as to science. 

 It is already certain that coal cannot be obtained without the release of this 

 gas, in variable quantities ; and it would appear from that experiment that the 

 chief if not only source of danger lies in the difficulty of collecting the whole 

 of it into the apparatus employed for that purpose ; that which escapes over 

 being found to exert its most formidable explosive powers as soon as it has 

 united with itself nine times its own volume of atmospheric air. As, however, 

 this is artificially supplied to a Mine, the problem of preventing the insidious 

 process of a union so disastrous may not be so hopeless as it might otherwise 

 appear. We have already harnessed the lightning to our service, and compelled 

 it to make its pathway under the ocean ; and if this gas can be so bitted and 

 bridled to its proper use, instead of venting itself in wild mischief, its value 

 would be enormous. It is manufactured by nature's laboratory, without retorts, 

 or stokers, or machinery, on a scale of magnitude of which we hardly can form 

 a calculation ; but it would appear that there is a ready-made store of gas in the 

 mines sufficient to light them up effectually, and at the same time remove an 

 ever present and accumulating source of danger to health and human life, It 



