METEOROLOGICAL INSTRUMENTS. 143 



made at suitable intervals before the water rises in the 

 gauge. 



It is important that the measure be taken without delay 

 after every fall of rain, as experience has proved that the 

 water in the gauge will soon become diminished by the 

 rising along the inside of the gauge by capillary attraction, 

 and then become dissipated by evaporation. 



The usual precaution must be observed in giving the rain 

 gauge such a position as that nothing may obstruct the rain 

 in its most oblique direction from entering it, and no 

 sediment must be suffered to remain in it. 



The rain gauge must be kept remote from all elevated 

 structures, to a distance at least equal to their height, and 

 still farther off where it can be conveniently done, and be not 

 more than ten feet above the surface of the ground. 



In freezing weather, when the rain gauge cannot be used 

 out of doors, it may be taken into a room, and instead of it 

 a tin vessel should be procured for receiving the snow or 

 sleet that may fall ; this vessel must have its opening ex- 

 actly equal to that of the rain gauge, and widen down to a 

 sufficient depth, with a considerable slope. It should be 

 placed where nothing can obstruct the descending snow 

 from entering it, and where no drift snow may be blown 

 into it. During a continued snow storm the snow may be 

 occasionally pressed down into it. The contents of the 

 vessel must at proper times be melted over a fire, and the 

 water produced poured into the gauge to ascertain its con- 

 tents, which must be entered in the gauge column of the 

 register. Price, $2.50. 



Cylindrical Rain Gauge. (Fig. C23, next page.) This 

 instrument is a cylindrical vessel, about four feet high, 

 and three and a twelfth inches in diameter, mounted on a 

 base resembling the segment of a cone ; the lower diameter 

 of which is thirteen inches, the upper three and a twelfth 

 inches, and the height eight inches. The base may be filled 

 with sand, or other heavy material, to make the instrument 

 steady ; and the general form being that of an upright 

 pedestal, it is a neat ornament for the garden or pleasure 

 grounds. At the top of the cylinder is an open basin, cor- 

 responding with the base, having an aperture one-twelfth of 

 an inch in diameter. The depth of the rain is indicated by 

 a graduated glass tube, communicating with the bottom of 



