GENERAL METHODS OF INVESTIGATION, BY S. STRICKER. IX 



cations can be made through the caoutchouc tubes, and the 

 forceps removed. This temporary and easily deranged chamber 

 will not prove satisfactory to those who are constantly working 

 with gases ; by them it will be found better to cement the con- 

 ducting tubules of glass once for all into grooves cut in the 

 slide. The spaces left can be filled up with putty. 



Fig. i. 

 n 



_J OIL 01 L_ 



Gas chamber, natural size. A, bird's-eye view ; B, longitudinal section 

 through the middle line ; a a, wall ; b b, conducting tubes. 



A slide which is to be used for such investigations with gas 

 must be attached to the stage of the microscope, because the con- 

 ducting tubes pull upon it, and so render the object liable to 

 be displaced. The gas should be transmitted from washing 

 flasks fixed on the stage, so that there may be firm supports 

 between them and the microscope, whilst they are themselves 

 connected with gasometers at some distance from the stage. In 

 my own investigations, in order to be able to dispense with 

 the services of an assistant, and use both my hands at the stage 

 for microscopic purposes, I have arranged my gas apparatus 

 beneath the table in such a way that I can effect the passage 

 of gas in one direction or the other by means of a treadle. If, 

 for instance, I wish to transmit carbonic acid gas, I so arrange 

 the apparatus, shown in fig. n., that the flask containing 

 hydrochloric acid gas can be raised by a string attached to the 

 treadle, and passing over pulleys. From the evolving flask 

 M a caoutchouc tube leads to my fixed wash bottle w, and 

 from this another tube passes to the microscope. The con- 



