On a Quantitative Blowpipe Assay of Chromium. 387 



vaporg; and it was established by tlie experiments of Becqiierel 

 as well as those of Gay Lussac and Blot that the electricity of 

 the atmosphere increases in strength with the altitude. 



A manifest relation, moreover, between the electricity oi the 

 atmosphere and the oscillations of the barometer has frequently 

 been observed, Humboldt^ treaiing upon the subject in his Cos- 

 mos, remarks amono; other tbin^^s that the electricitv of the at- 



o o 



niosphere, whether considered in the lower or tlie upper strata 

 of the clouds in its silent problematical diurnal course, or in the 

 explosion of the lightning and thunder of the ternpestj appears 

 to stand in a manifold relation to the pressure of the atmosphere 

 and its disturbances. 



The tidal movements of our atmosphere produce regular sys* 

 tematic compressions twice in twentv-four hours. These occur 

 With so mtich regularity within the tropics, as observed by Hum- 

 boldt, that the time of day is indicated within fifteen or twenty 

 niinutes by the state of the barometer. And Saussure observed 

 a diurnal change in the electricity of the atmosphere correspond- 

 ing with the diurnal changes of the barometer. The electricity 

 of the atmosphere, he observes, has therefore a daily period like 

 the sea, increasing and decreasing twice in twenty-iour h«nir3. 

 It, generally speaking, reaches its maximum intensity a few 

 hours after sunrise and sunset, and descends again to its minimum 

 before the rising and setting of that luminary. 



Other phenomena, which it is believed may be traced to the 

 same cause, will be the subject of another communication. 



Art. XXIX,— On the Quantitative Assaj/ of Chromium ly BIoiv 

 pipe Processes; by EuGENE W. Hilgard, Ph.D. — (Abstract.) 



(Comtnunicated at the Montreal meeting of the American Association, Aug., 1857.) 



r 



The quantitative determination of chromium has thus far 

 been mostly confined to the laboratory. The processes employed 

 Were rather long, especially when many other elements occur- 

 red with the chromium, giving rise to a great variety of meth- 

 ods, requiring apparatus too voluminous to be carried in the 

 field. No general method sufficiently simple and exped^t'ous 

 for practical purposes has been devised — methods such ns Ave 



d M'hich the genius of 



possess for most of the nseful metals, an 

 •Piattner has so admirably adapted to perf 



formance bv the aid of 



*he blowpipe. Expedltiousness of 

 9f the utensils required, are the characteristics of these pn>ce88e3 

 of Piattner, and the main conditions of their practical useful- 

 ness; and it is to the exclusive employment of the dry way that 

 these advantages are mainly owing* 'The metals being,^ after a 



