If in towns the ever increasing accumulation of gas, of water, and of drainage pipes constitutes a danger against the efficacy of lightning conductors--to be guarded against only by frequent testing--there is another source of danger arising in the country. It is in the planting of new trees and the growth of old ones which is constantly going on in the vicinity of the thousands of country houses and mansions with which Great Britain is dotted from one end to the other, more than any other country in the world. The fact has already been dwelt upon, that trees are more liable to be struck by lightning than any other natural objects, the reason of it being unknown, except in the very probable surmise that the moisture in them forms the natural cause why the electric force seeks its path through them to the earth. Whatever the cause or causes, there can be no doubt that trees are incessantly struck by lightning, and that they are the more exposed to be struck the higher they are and the wider the extent of their branches. Consequently, wherever trees are being planted, or growing up around houses, the greatest care should be taken in designing lightning conductors, so as to provide against the action exercised by them in juxtaposition to the electric force. Thus, if trees, originally small, should reach to such a height above dwellings as to make it possible that a stroke of lightning will fall upon them, in preference to the conductor, the arrangements for protection will have to be altered, so as to ensure the safety of the house nearest these particular trees. Again, if, as often happens, there are new trees planted near a building the side of which has no protection whatever, such as a greenhouse or conservatory, the conductor should be extended in this direction. In connection with trees, mention must be made of wells and fountains, as possible dangers to the proper action of lightning conductors. Many a disaster has been caused by newly-made wells to dwellings which were previously well protected by conductors. The only safeguard against danger arising from these and numerous other causes, which it would be tedious to specify, lies in careful, constant inspection and testing of conductors.