Admiral Fitzroy&rsquos Rain-gauge
A form of rain-gauge, very well adapted for expeditious observation at any time, has been designed by Admiral FitzRoy, and extensively employed by his observers. It is cylindrical in shape, with the funnel let into the top; and the rainfall is collected in an inner and much smaller cylinder, so that a small fall is represented by a considerable depth of water in the gauge. The amount of rain which has fallen is ascertained by a dipping tube, similar in principle to the dipping syphon used
by gaugers for taking out specimens of wines or spirits from casks by simply removing the bung. A short, vertical, tubular opening provided with a cap, which is attached to the instrument by a chain that it may not be lost, is formed in the funnel. The measuring tube, which has a small hole at each end, should be placed upright in the gauge; then the thumb should be pressed over the upper aperture, while the tube is lifted gently out, holding in the lower part a quantity of water representing the depth of the rain in the gauge, the upper edge of which is at the mark to be read off. The glass tube is graduated to inches and tenths; hundredths of an inch can be readily estimated by the eye. The marks are fixed by actual trial with a standard gauge, and are artificial, not true, inches.