218 Instructions for the ScientifiG Expedition 



one inch depth of rain in the gauge will be measured by 100 inches 

 of the graduated vessel, and Tu'ou th inch of rain may be very easily 

 read off. 



It is very much to be desired that, being of such easy construc- 

 tion, more than one of these gauges should be erected, or at least 

 one placed with its edge nearly level with the ground, and another 

 upon the top of the highest building, rock, or tree in the immediate 

 vicinity of the place of observation, the height of which must be 

 carefully determined ; it having been satisfactorily ascertained that 

 the height of the gauge above the ground is a very material element 

 in the quantity of rain which enters it. The quantity of water should 

 be daily measured and registered at 9 a.m. 



7. Clouds and Meteors. 



Many very highly-interesting observations may be made, without 

 the aid of instruments, upon the clouds. In describing them Mr. 

 Howard's nomenclature may be adopted with great advantage. By 

 means of the clouds different simultaneous currents of wind may 

 often be detected, the different directions of which should be care- 

 fully ascertained by referring their motions to some fixed object. 

 Their gradual evaporation or precipitation should also be carefully 

 noted, and particularly their regular disappearance at night, or their 

 more irregular and sudden formation. 



Rainbows, parhelia, haloes, &c., will of course be noted amongst 

 the occasional remarks of the register ; and an attempt should be 

 made to express approximatively by numbers, the proportion which 

 the overcast portion of the sky may bear to the clear space. For 

 this the hemisphere may be supposed to be divided into eight sec- 

 tions, and the cloudy portion may be expressed by the fraction ^th 

 or f ths, &c. 



8. Electrometers. 



The Council are fully impressed with the high importance of 

 regular observations on the electrical state of the atmosphere ; but 

 they are not prepared to suggest any means of effecting this desirable 

 object, which will at all correspond with the present advanced state 

 of electrical physics. At no distant period they hope to supply a 

 defect which is certainly a reproach to science. In the meantime 

 much valuable information might be acquired by observations of an 

 electroscope, on one of the ordinary constructions connected with a 

 lofty insulated wire. 



In erecting such a wire, proper precautions should be taken against 

 accidents by preparing a sufficient conductor in its immediate vici- 

 nity, by which a communication could be at once opened with the 

 ground in case of any sudden and dangerous accumulation of the 

 electric fluid. 



As a temporary contrivance, a common jointed fishing-rod, having 

 a glass stick well varnished with shell lac, substituted for its smallest 

 joint, may be projected into the atmosphere. To the end of the 



