64- Notices respecting Nciv Books. 



introduced the fluid to b and sealed tlie end a, the endywas raised 

 till it was the highest point, the fluid in the lower extremity heated 

 until combustible vapour issued at J', and then a small flame applied 

 whilst the temperature of the other parts was allowed to fall; the 

 vapour within soon condensed, the extremity was instantly closed 

 by the lamp, the lamp itself removed, and the tube left hermetically 

 sealed. Then collecting all the fluid to the end d, the distillations 

 and rectifications were performed, and when fluid had collected in 

 e, it was easy by opening the end /under mercury, to ascertain 

 whether it vvas sufficiently volatile to rise as gas at ordinary pres- 

 sure, and when it did so the gas was easily collected in jars. 



" It will be unnecessary to refer minutely to the capability of trans- 

 ferring backwards afforded by different indications of the parts of 

 the tubes ; by angles different to those mentioned, the fluid may be 

 nt first returned from e to d, then from d to 



c, and so on. By bending the tube at /, 

 as is represented in the accompanying 

 wood-cut, so that the tube from / to n 

 shall be in a plane perpendicular to that 

 which includes the part from g to /, the 

 power is obtained of returning the products from k to h, or from m 

 to k independently of each other; and thus the more fixed and 

 more volatile parts may both be returned and be re-distilled with- 

 out mutual interference. The student will easily comprehend these 

 forms of tubes and their advantages by bending apiece of wire into 

 the directed or desired shape, and observing the position of its parts 

 as he inclines it in different directions." 



Would room admit of it, there are various other parts of the work 

 which we should have great pleasure in presenting to the reader ; 

 but we must now conclude with a few and only a few very miscel- 

 laneous observations. 



First, as to filters and funnels : — It would, we think, be well to 

 warn the tyro that if a single drop of water remain in the funnel, the 

 filter is extremely liable to tear at that spot. The subject of filters 

 is one which is extremely puzzling to the young experimentalist, 

 and we think a little more might have been advantageously said 

 with respect to double filters, — as to the mode of cutting, weighing, 

 and drying them, and allowing for the quantity of any product 

 which adheres to the filter. We believe it is not generally known, 

 or if known not adverted to, that if a sheet of filtering paper be 

 divided even quite accurately into equal portions, in the direction 

 in which It is folded, one half is heavier than the other, — a circum- 

 stance which arises from the manner in which the frame is held 

 during the luanufacture of the paper. Now it is extremely convenient 

 and saves much weighing and cutting, that filters of equal weights 

 should as nearly as possible be of equal .sizes : with this intention it 

 is better not to divide the sheet into halves, but to cut the portions 

 of which the double filter is to be made, across the sheet of paper. 



In p. 172. excellent directions are given on the very simple sub- 

 ject of glass stirrers, to which however we would add one hint more ; 

 — they are extremely apt to roll from the experiment-table. Now 



this 



