Page:St. Nicholas, vol. 40.1 (1912-1913).djvu/664

464 operates the gears, which raise the two bronze spindles that pull the plug or gate up into the top of the valve, called the “cap” or “bonnet.”

The small, sixteen-inch valve on the side of the large valve is what we call a by-pass valve, and which, when opened, relieves the pressure, so that the large gate can be opened more easily.

The opening of these great valves is so large that, if a floor were laid inside it, a forty-horse- power automobile could run into or through it.



I think that the chief cause why ice melts more quickly about the edge of a pond than the rest of it, is that the surrounding earth is warmer than the water farther out. This is due largely to the fact that the darker-colored earth absorbs the sun’s heat much more than ice. This effect is seen when gravel is on the ice and exposed to sunshine. The stones are heated so much that they melt holes down into the ice.

That shallow water would warm up more quickly than deeper water is undoubtedly true, especially after the ice has gone at the edge, for the ice certainly reflects the sun’s heat more than the water does, so that the ice would tend to keep on melting around the edge of the pond.

The color of the hair is due to iron. which is picked up by the cells of the hair follicle in the little factory in the skin where hairs are made. As one gets older, the little cells which work at manufacturing hairs grow weary, and they will not take up as much iron as they once did.—.
 * Why does a person’s hair grow white with age?


 * I send you inclosed some photo graphs that I thought would be interesting to “Nature and Science” readers. I also want to ask some questions about some of them.

is a picture of an approaching storm taken with a color screen.

was taken at night, during a thunder-storm. It was exposed about five minutes.

was taken immediately after No. 2, and was exposed about eight or ten minutes. I would like to ask why some streaks are black and some white.

was taken at night, when there was mach flash lightning but few streaks. It was exposed fifteen or twenty



minutes. Can you account for the streaks on it? I am sure it was open only while at the window. The two impressions of the windmill are because I moved the camera slightly as I went to close the shutter.

All these pictures were taken with a No. 3a folding .