640 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



sure. At the end of that time there was less scale in the steel than in the 

 iron boiler. The steel boiler generated 25 per cent, more steam and evapo- 

 rated an average of 11.66 cubic feet of water per hour; the iron evaporated 

 9.3t cubic feet. The quantity of coal consumed per 12 hours was 2,*I06 

 for the steel, and 2,972 for the iron boiler. The plates of the steel boiler 

 directly over the fire were found to be uninjured, while those of the other 

 were worn out. The advantages of the steel boiler are strength, lightness, 

 rapidity of evaporation, durability under heat, the securing of more perfect 

 riveting, and comparative freedom from scale. 



The Production of Oxygen without Heat. 



Mr. J. Robbins has explained before the London Chemical Society the 

 process used by him for obtaining pure oxygen. The combinations made 

 by him are not original, yet they may not be generally known among those 

 who separate and use this gas. The 'compound used is the peroxide of 

 barium and bichromate of potash. It is placed in a glass flask or bottle 

 provided with an exit tube, and a mixture of dilute sulphuric and hydro- 

 chloric acids is poured on, when the oxygen is rapidly evolved. Peroxides 

 of potassium, sodium, strontium, and calcium, may be severally substituted 

 for the peroxide of barium. And manganate or permanganate of potash, 

 binoxide of manganese, and binoxide of lead, may be used in the place of 

 bichromate of potash; but the cost of these articles renders the latter most 

 available. The chemical changes in this process not readily explained are 

 the formation of the sulphate of baryta and peroxide of hydrogen, or oxy- 

 genated water; this, in contact with chromic acid, is reduced to water, and 

 the sesquioxide of chromium is formed; oxygen gas being disengaged from 

 both substances, quite pure, and fit to be used for medical purposes. 



Ink-Plant. 



Prof. Jameson, of the University of Quito, states that the expressed juice 

 of the berries of the coriaria thymifoUa is u^ed by him in preference to the 

 ordinary ink, because it does not corrode the steel pen. There is a tradi- 

 tion that during the Spanish administration documents written with this 

 juice and the common ink, were sent to the mother country. During the 

 voyage around Cape Horn the documents got wet; those written with ordi- 

 nary ink became nearly illegible, while those written with the vegetable 

 juice remained unaltered. A decree was afterward issued that all Govern- 

 ment documents should be written with Chauchi, the name of the juice. 



The Electric Fly. 



Mr. Charles Tomlinson communicates to the PhilosopMcalJournal an inter- 

 esting account of many experiments made by him with the little instrument 

 used in connection with an electrical machine called the electric fly or mill, 

 or tourniquet, which is formed of two or more metallic radical arms, having 

 their extremities bent at right angles and brought to a fine point. As a 

 preliminary explanation why he has made these experiments, he gives 

 various opinions of philosophers as to the cause of its action. After detail- 

 ing its backward revolutions in the open air and under a glass vase, its 

 inaction in rarefied air, its increased action in turpentine, benzole and paraf- 

 fine oils in both directions, and its forward motion in the air after a modi- 



