Page:Popular Science Monthly Volume 7.djvu/418

From Wikisource
Jump to navigation Jump to search
This page has been validated.

ing of the jar, and the other on the knob (A), the gold-leaf will be destroyed. If, for the strip of gold-leaf, a wire the one-thirtieth of an inch in diameter be substituted, the charge will be carried off without its doing any damage. Here we see that, while the electricity was at rest (static), the gold-leaf was quite, capable of receiving as heavy a charge as the most powerful machine could impart; but, the moment the electricity began to flow (became dynamic), the gold-leaf was destroyed, notwithstanding its great surface, while a wire of far less surface afforded a perfect way for the charge to pass off.

Experiments in this direction might be multiplied ad infinitum, and, when properly conducted, they all lead to the same conclusion, which is, that, when made of the same metal, the efficiency of any rod is in direct proportion to its weight per foot. It may be round, square, tubular, ribbon-like, or in the form of a rope consisting of several strands; it makes no difference. For ourselves, we give the preference to a simple flat ribbon as being most easily applied and less obtrusive, but wires and wire ropes are very convenient, more easily procured, and quite as good.

That M. Nouel has neither experimented upon the subject nor given deep thought to it, is evident from the fact that he advises us to substitute hollow pipes for the present solid rods. As the interior surface of a pipe is incapable of receiving a charge of static electricity, it is evident that, if this law applies to lightning-conductors, the capacity of a pipe or tube would be just doubled by slitting it and spreading it out flat.




EDUCATORS, to-day, are divided into two schools, especially with regard to colleges and universities. The older of these schools insists very vigorously upon the importance of thorough instruction in the so-called "dead languages," and makes all else subordinate to them. The new school, on the other hand, the school which seems to be steadily gaining ground, upholds the claims of the sciences, and gives to them the places of honor in every general course of study. The controversy between these schools is well worn, but has not yet become threadbare. The questions at issue cannot grow stale and hackneyed until after they have been finally settled.

In discussing all such questions many commonplaces must be uttered. Indeed, much confusion has arisen among educational writers because they have too timidly feared to seem commonplace. These commonplaces are the necessary, rough foundations upon which