Franklin's rod, erected over his house in the summer of 1752, was evidently intended by him for experimental rather than protective purposes. There is no doubt whatever in his mind about the use of such pointed conductors for the protection of buildings and ships against the destructive effects of lightning. He expressly says, in an article printed in _Poor Richard's Almanack_ for 1753, that "It has pleased God in His infinite goodness to mankind, to discover to them the means of securing their habitations and other buildings from mischief by thunder and lightning. The method is this: provide a small iron rod (it may be made of the rod-iron used by the nailers), but of such a length, that one end being 3 ft. or 4 ft. in the moist ground, the other may be 6 ft. or 8 ft. above the highest part of the building. To the upper end of the rod fasten about a foot of brass-wire, the size of a common knitting needle, sharpened to a fine point; the rod may be secured to the house by a few small staples. If the house or barn be long, there may be a rod and point at each end, and a middling wire along the ridge from one to the other. A house thus furnished will not be damaged by lightning, it being attracted by the points and passing through the metal into the ground without hurting anything. Vessels also, having a sharp-pointed rod fixed on the top of their masts, with a wire from the foot of the rod reaching down round one of the shrouds to the water, will not be hurt by lightning." It is well known, as Dr. Rotch, Director of the Blue Hill Observatory, recently pointed out, that the matter for these almanacs was prepared by Franklin himself under the pen-name of Richard Saunders. As the above passage appeared in the almanac for 1753, it is obvious that it must have been ready sometime toward the end of 1752. Furthermore, we know that it was actually in the hands of the printer in the middle of October of that year, for the _Pennsylvania Gazette_ of Oct. 19th says that the almanac was then in press and that it would be on sale shortly. Whence it follows that the year 1752 is the year of the invention of the lightning rod, and not 1753 or 1754 as often stated. The instructions given by Franklin include all the essentials necessary for the erection of a lightning conductor. It may be made of iron or copper, flat or round, but must make good "sky" and good "earth." The former condition is secured by screwing to the top of the rod either copper or platinum terminals ending in sharp points; and the latter, by burying the lower end deep in moist soil. Between "sky" and "earth" the rod must be continuous.