given on a late Trial, 319 



mi^ht be kept in a state of constant ebullition without danger 

 or difficulty. 



For the sake of avoiding any misapprehension respecting the 

 construction or use of this apparatus, an engraving of it is at- 

 tached to these observations, by which the use of each part 

 will appear, and the advantages will be obvious, which must 

 result from the employment of such an apparatus in boiling 

 sugar or other substances, liable to be injured when exposed in 

 metallic vessels to the direct operation of the fire. 



It is observable, that in this process there is no fire under- 

 neath the sugar-pan, but at a short distance there is a fire-place, 

 and over that a wrought-iron vessel containing the whale-oil, 

 which does not boil at a temperature much below 650° or 700*^, 

 In the top of the oil-vessel a thermometer is fixed, as shewn in 

 the drawing, the tube of which is sufficiently long to allow the 

 mercurial bulb to sink beneath the surface of the oil. It is of 

 importance to remark, that this thermometer is graduated only 

 to 450° ; consequently, if the oil were to acquire a tempera- 

 ture much beyond 450^, the tliermometer would burst, and the 

 circumstance of the increased temperature would in a moment 

 be discovered, before any mischief could possibly arise from 

 the accident. 



In using this apparatus, the pump is set to work as soon as 

 the oil attains a temperature of 350°; and thus a portion of 

 the oil is forced from the iron vessel into the tube G, whence 

 it rushes through the coil of pipe lying within the copper pan ; 

 and from the copper pan it returns again and again, like the 

 circulation of the blood, into the iron vessel. The heated oil 

 passing in this way through the fluid sugar, boils the syrup, 

 and that at a temperature very far below the boiling point of 

 fixed oil, so that there appears to be no risk in the process. 



However, when tJie conflagration had broken out upon the 

 premises, and there was no clue to the origin of the fire, it 

 was suggested by some of the Insurance Companies, that it 

 might have been occasioned by the heated oil ; although they 

 did not at that time venture to say how. Yet as the payment 

 of the sums insured might have been avoided, if it could have 



