OF ARTS AND SCIENCES: MARCH 8, 1864.* 253 



having the column of asbestos of considerable length, the anterior end 

 of which only is ignited, the substance, if volatile, becomes diffused 

 through a large space, and the distillation thereby easily controlled ; as 

 only a small portion of the substance need then be heated at a time. 

 Doubtless a shorter tube would answer equally well for many non- 

 volatile substances. It will be observed that the asbestos packing is but 

 another application of the principle involved in the use of wire gauze 

 in Davy's safety-lamp.* 



In order to obtain perfect control of the analysis, and to be always 

 certain that the requisite quantity of oxygen is being admitted, I have 

 adopted certain simple expedients, enumerated below, which have been 

 found fully adequate to that end. 



1. The distillation of the substance, if volatile, is effected by means 

 of a bar of copper, placed over and attached to one of Bunsen's burners, 

 as shown at a, in the accompanying figure. 



This bar, having first been brought to the maximum temperature 

 which the lamp is capable of producing, is placed near or under the 

 bulb containing the substance ; applying that part of the bar nearest or 

 most remote from the flame, or an intermediate point, according to the 

 temperature required. 



The steadiness of the heat thus applied, and the faciUty with which 

 it may be regulated, by simply moving the bar, render it decidedly 

 preferable to any other means which I have employed for that purpose. 

 I had for a long time used such a bar for the same purpose in the old 

 process, with extreme satisfaction. In some cases a bar of copper laid 

 on the combustion furnace,! one end projecting into the flame by which 



* It has occurred to me that my safety-tube may serve as the basis of a more 

 simple and equally accurate process for the analysis of gases, by gradual com- 

 bustion, instead of explosion; in which weighing would take the place of measure- 

 ment. I propose, at an early day, to study this question by a series of experiments, 



t As there are those, and probably there are many, who still persist in the use of 

 charcoal in place of the more modern gas furnaces for generating heat for com- 

 bustions, I desire here to say that I have in use one of Baumhauer's gas furnaces, 

 procured a few years ago from Luhme & Co., in Berlin, which seems to me to have 

 no fault. It is impossible for me to conceive what objection one could have to it, 

 unless it be that a naked tube might become overheated along the bottom ; and 

 this would be a valid objection if the remedy were not so simple. If the tube be 

 laid in a trough of sheet iron (brass is objectionable, in my process, on account of 

 its obscuring the tube with oxide of zinc), with a thin layer of asbestos between, 

 and fastened together with wire, no harm can ever occur from overheating. A 

 VOL. VI. 25 



