Dictionary of Chemical Apparatus. 333 



lecting precipitates, drying, and weighing them ; and how cumsy, 

 slow, and inefficient are the proceedings of the uninitiated in those 

 trifling mysteries, compared with the accurate rapidity and efficient 

 delicacy of those who have acquired tact by practice ! 



We turned, in the Dictionary before us, to the articles " Filtering" 

 and " precipitating Apparatus ;" under the former, instead of finding 

 an enumeration of the little practical points to which we have ad- 

 verted, we are told, by way of definition, that " filtration is a finer 

 species of sifting ;" " that salt water cannot be deprived of its salt 

 by filtration, but muddy water may !" p. 111. After this curious and 

 useful information, reference is made to fig. 19, plate I., which re- 

 presents a "filtering stand," consisting of three legs, supporting a 

 horizontal board furnished with a hole," &c. Of the glasses for col- 

 lecting precipitates every shape, except the right one, is described: 

 " conical," it is true, they should be, but the base (and not the apex 

 of the cone as here stated) should be downwards. 



Theblowpipe is a very important instrument in the hands of the ex- 

 perimental chemist, and Mr, Children's translation of Berzelius' Es- 

 say upon it has communicated much valuable practical information 

 upon the subject of its use and applications ; but under the article 

 " Blowpipe," instead of a compendious abstract, which really would 

 have been useful, of the work we have just named, there is a great 

 deal of rhetoric wasted to prove that the cheeks, nostrils, lungs, and 

 mouth resemble a double bellows, while all that should have been 

 communicated to the learner respecting the various and indeed op- 

 posite effects of the different parts of the jet of flame are carefully 

 withheld. It is true, that to make up for this defect, Mr. Gurney's 

 oxydrogen blowpipe is described at length in three out of the two- 

 hundred-and-ninety-five pages before us. 



Underthehead " Mercurial-Pneumatic Trough," not a word is said 

 of Mr. Newman's excellent and economical form and construction of 

 that indispensable piece of apparatus, for which we refer our readers 

 to the FirstVolumeof this Journal, and which, since that time, he 

 has considerably improved. 



Under the article" Pneumatic-pump," or air-pump, a description 

 of the worst and most imperfect construction of that machine is 

 given, to the exclusion of all the various improvements which it has 

 lately undergone. We had hoped to have here found an account of 

 the principle sometime since adopted by Mr. Styles, of the London 

 Institution, by which a considerably more perfect vacuum is ob- 

 tained than by any other contrivance which we have seen adopted, 

 and of which we shall endeavour to procure a description; but the 

 author of this Dictionary has not even noticed the pumps with glass 

 cylinders and metal valves, as usually constructed by the best in- 

 strument-makers of Paris. 



Hygrometers of various kinds are copiously and pretty correctly 

 dwell upon, and the author lias made some amends for the intro- 



