TABLE OF CONTENTS 



TO THIS FOURTH VOLUME, 



APRIL 1800. 



ILnGRAVINGS of the following Objeas: 1. Mr. Bofwell's Ventilator on a 

 new Principle. 2. An Hydraulic Machine operating by compreffed Air; 

 and, 3. The Chemical Apparatus of Woulfe, put together without luting or 

 grinding. 



I. On the Antiquity of the Art of etching upon Glafs, by Mr. Fred. Accum. 



page 1 



Receipt for making an acid to corrode glafs, publiflied in 1725. Inveftigation of the, real inven« 

 tor, Henry Swanhard, of Nuremberg, in 1670. 



II. A Defcription of a new Inftrument called the Blaft Ventilator. Invented 

 by J. W. Bofwell. . . . - . p. 4 



A ftream of air being received through a conical mouth, and conduced through a fmaller cylin- 

 der, gives motion, by its lateral adllon, to the air in a larger furrounding cylinder. The cavity of 

 this laft is made to communicate, by means of a pipe, with the place required to be ventilated. 



III. Experiments on Whinftone and Lava. By Sir James Hall, Bart. F.R.S. 

 & F.A.S. Edin. - - - - - p. 8 



Obfervations on the geological fyftem of Dr. Hutton, particularly with refpe£l to the fiony cha- 

 rader and fradurc of granite, porphyry, and bafaltes. Probability that this charafter may be 

 the confequence of flow cooling and cryitallization. Experiments to prove that this is in fa£t the 

 cafe. Fufion and cooling of whinftones, in which it was found that fpecdy cooling produces 

 the vitreous charader, and flow cooling the ftony charafler. Treatment of lavas in the fame 

 manner. 



IV. On the Hydraulic Machine erefted at Schemnitz in Hungary. p. 1 8 



Vol. IV.— March 1801. b ' Two 



