180 SCIOPTICON MANUAL. 



nuts are hard to start ; take a piece of wood, sharpened 

 at one end, insert it in the cylinder, and break up the 

 residuum by a few vigorous blows ; pour it out and re- 

 charge without either washing or drying. 



" To operate the cylinder for hydrogen, unscrew the cap as 

 before, put in two pounds of scrap zinc, and add a mix- 

 ture of sulphuric acid and water (four pounds of acid 

 and four quarts of water). This mixture should be cold 

 when poured into the cylinder. As soon as the liquid is 

 poured in, screw down the cap as before, slip a gum tube 

 on the nipple, and begin to use as soon as there is suffi- 

 cient pressure, if it is desirable. There is no practical 

 use for the meter in this case; if used, the red liquid 

 will stand within about a quarter of an inch of the top 

 of the tube when the operation is completed. 



" As there is an excess of zinc introduced all the acid 

 will be neutralized. There will be no deterioration of 

 the gas or injury to the cylinder from long standing. 

 When the hydrogen is burned up, pour in water to dis- 

 solve the sulphate of zinc. This is easily done, and the 

 cylinder is then rinsed out, and is ready for another 

 charge." 



We believe with the inventor, as above expressed, 

 that the self-condensing gas cylinders will prove a very 

 great convenience in the production of the liine light. 



It is obvious that the directions as to fitting the cap 

 upon the cylinder-head must be strictly observed. Any 

 particles between the meeting surfaces prevents perfect 

 contact and so will allow the gas to escape. 



The oxygen cylinder, owing to its thickness, requires 

 a longer heating to disengage the gas than the retort 

 before described. There is, in this case, no outward 

 current of gas, dust, or foam, to make former directions 

 applicable only so far as repeated above. 



