given on a late Trial, 353 



Guildhall, on the 13th of this month; and, as it is expected 

 that one trial will settle the question as to the remaining po- 

 licies, the whole will, probably, be decided before these animad- 

 versions are published. Should any thing, however, occur on 

 the ensuing trial that is new and interesting, I may, probably, 

 deem it necessary to trouble the editor with some farther ob- 

 servations. S. P. 



Description of the Plate. 



Fig. 1. — Is an elevation of an apparatus for boiling sugar, 

 or evaporating any liquid by means of the circulation of heated 

 oil. 



A, is a wrought-iron vessel for heating the oil, similar to the 

 boiler of a steam engine. It is set in brick work, with a fire 

 under it of a moderate size, and without any flues round the sides, 

 so that the whole action of the fire is upon the bottom. It is 

 made of an oblong form, and its length should exceed its 

 breadth as much as the situation it is to be placed in will allow. 

 The size depends upon the quantity of oil to be heated, or the 

 liquor which is to be evaporated ; and it is observable that the 

 more the surface presented to the fire exceeds the evaporating 

 surface, the greater will be the economy of fuel. Whale-oil, 

 free from sediment, is found to answer better than any other for 

 this purpose, and the quantity necessary to be employed, is 

 merely sufficient to cover the bottom of the vessel to the depth 

 of six or eight inches. 



B, is a thermometer for ascertaining the heat of the oil. 



C, is a small tube opening at the lower end into the oil vessel, 

 while the upper extremity passes into a long flue, called a steam 

 vent, and communicating with the atmosphere. This pipe 

 serves three different purposes : the first is, that before the 

 pump begins to work in the morning, there is a quantity of air 

 contained in it, and it is necessary there should be a vent for 

 that, when the pump is set to work, in order to prevent any 

 compression in the inside of the vessel. The next is, that with 



