3G2 Analt/sis of Scientific Books. 



will be evolved*" This absurd enunciation is for some unknown 

 reason, printed in italics. He evidently does not know, that 

 when the density of a body is increased by any means, its bulk 

 becomes less, and vice versa ! 



The chapter on specific gravity, is stuffed out with common- 

 place and ill-arronged details on the art of swimming, diving 

 bells, weather-glass(;s, balloons, and air-pumps. 



Chapter 18, entitled " Colouring and Bleaching ," contains an 

 unmerciful and unacknowledged plagiarism from a theoretical 

 article on Dyeing, in the first supplement to the Encyclopedia 

 Britannica. It can be of no service to the artisan. 



" Exp, 867. Bleaching by means of the Oxymuriatic gas." 

 Towards the end of this article we have the following precious 

 recipes. " The proportions observed when cotton is to be 

 bleached, are manganese 30 parts, common salt 80, sulphuric 

 acid 60, water 120. For linen cloth the proportions are as 

 follow : manganese 60 parts, salt 60, sulphuric acid .50, water 

 50." We should be glad to know why 30 parts of manganese 

 are sufficient for 80 of common salt in the first case, and 60 are 

 required for 60 in the second. Nothing can place in a clearer 

 light than these recipes, the irrational and dangerous empiricism 

 of his pretended prescriptions for manufacturers. Again, "Exp. 

 870. To bleach by means of the sulphuret of lime." This old 

 project of Mr. Higgins, was very unfortunate. If Mr. Mac- 

 kenzie will take the trouble of inquiring of any intelligent Irish 

 linen bleacher, (and there are many who understand chemistry 

 infinitely better than he does,) he will find that the linen trade 

 received such a shock by the employment of sulphuret of lime, 

 instead of barilla, as it did not recover in reputation for several 

 years. An immense deal of cloth was ruined by this notable 

 recipe. Mr. Mackenzie's directions to bleachers remind us of 

 those of an eminent agriculturist, (not less profoundly versed 

 in practical chemistry), to farmers, who having heard of a plan 

 for preventing the ravages of the fly in turnips, part of which 

 consisted in steeping the seeds in a solution of chlorine : and 

 having, moreover, heard that chlorine was produced by a mix- 

 ture of oil of vitriol, salt, and manganese, committed the 

 trifling chemical error of directing the seeds to be steeped in 

 this mixture ; a perfect cure, no doubt, for the fly, or any other 

 evil to which the crop might have been liable. 



" Exp. 997. Copal Varnish. Reduce to powder an ounce of pure 

 carbonate of potash, and then lay it before the fire till it becomes 

 hot and dry. In this state put it into a pint of alcohol, or oil of 

 turpentine. All the watery particles contained in the oil, or 

 spirits, will be absorbed by the alcali ; and the alcohol, or turpen- 

 tine, will thus become pure, or highly rectified. This process is 



• Page r.-19. 



