Where fires have been traced to spontaneous combustion, it has generally been found that some kind of decomposing vegetable matter has been the active instrument in their production. Cotton-waste which has been used for cleaning oily machinery and then thrown aside in some forgotten corner, sawdust on which vegetable oil has been spilt, and hemp, have each in its turn been convicted of incendiarism. The simple remedy is _to avoid the accumulation of lumber and rubbish in places where valuable goods and still more valuable lives are at stake_. Occasionally fires have been accidentally caused by the concentration of the sun's rays by means of a lens or of a globe of water, and opticians have for this reason to be very careful in the arrangement of their shop-windows. A case lately occurred where a fire was occasioned, it was supposed, by a carafe of water that stood on the centre of a table. The sun's rays had turned it into a burning-glass! It is stated, with what amount of truth we cannot say, that fires in tropical forests are sometimes caused by the heavy dewdrops attached to the foliage acting the part of lenses. The advance which has been made during the last twenty years in all appliances connected with the art of extinguishing fires, has done much to limit or rather localise the dangers of such catastrophes; for whereas in the old days the lumbering 'parish squirt' was the only means of defence, we have now in all large towns steam fire-engines capable of throwing an immense stream of water with force enough to reach the topmost floors of very high buildings. The aforesaid 'squirt' was capable of little more than wetting the outside of contiguous buildings, with a view to prevent the spread of the original fire, which generally burnt itself out. But now our engines furnish a power which will often smother a large fire in the course of half an hour or less. Moreover, our well organised fire brigades are trained to convey the hose to the nucleus of the flames, and much heroism is shewn in the carrying out of this dangerous duty. It will be especially interesting to the readers of this _Journal_ to note that the first really efficient brigade was formed in Edinburgh by the late lamented Superintendent Braidwood. He was afterwards employed in a like service for London, where his devotion to duty eventually cost him his life. Like a true soldier, he died 'under fire.' And now for a few simple precautions.