1872.] 



Evolution of Life from Lifeless Matter. 



143 



file being previously made upon it), hydrogen flows into the vacuous tube. 

 Both clips are now closed, and by means of forceps, the hand being be- 

 neath the bell-jar, the lower end of the tube is broken off. No liquid, how- 

 ever, escapes, because the internal pressure is not much in excess of that of 

 the atmosphere. The condition of things now can be explained only by the 

 aid of a drawing (fig. 5) : the whole arrangement consists of a pipette con- 

 taining the experimental liquid above and below, which is an atmosphere 

 of hydrogen ; each drop of liquid expelled is received on a slip of glass in 

 such an atmosphere. A drop of liquid is deposited by squeezing the space 

 of india-rubber between the two clips, that clip nearest the bell-jar being 

 open ; before removing the pressure, it is again closed, and the partial 

 vacuum made by compressing the india-rubber is filled up by allowing gas 

 to flow in from the apparatus. This precaution prevents the possibility of 

 the atmosphere of the bell-jar bubbling up into the tube after a little fluid 

 has been discharged. 



3rd. Treatment of the glass slips. — These are heated in an air-bath to 

 about 200° C, taken out while hot with forceps, and placed on the stage 

 in the hydrogen to cool, and kept there till wanted. 



4th. The glass covers. — These are washed in the acid-dichromate solu- 

 tion, then in distilled water, and finally in alcohol, and, being picked up by 

 a pair of peculiar forceps, are heated over an argand burner till very hot ; 

 they are then held in the glass vessel full of gas till cool enough to use. The 

 forceps I devised (fig. 6) have points of watch-spring steel, so that a thin 

 glass cover may be firmly gripped without breakage. They are made by 

 cutting a small pair of crucible tongs an inch or so before the part where they 

 bend at right angles ; they have then two pieces of thin brass rivetted on, 

 which are bent at right angles an inch or so from their ends ; the points are 

 made by rivetting on pieces of watch-spring steel a little more than an inch 

 in length. When these tongs are held in the position of scissors, that is to 

 say with the thumb above the fore finger, the ends point downwards. To 

 take up a glass cover, the forceps being in the position mentioned, the 

 wrist is turned over from right to left while the elbow is raised, the glass 

 resting on the lower point while the upper is closed down on it, may be 

 safely held and conveyed to where it is wanted. After a little practice 

 these pincers are easily used. 



The advantage of the bung closing the neck of the bell-jar being bored 

 eccentrically is, that by simply turning the bell-jar horizontally the pipette 

 point delivering the liquid may be shifted from a glass slip on which a drop 

 of liquid has been deposited to another clean one, or be made to turn 

 through such an angle as to be out of the way of the glass stage, in order to 

 transfer the solution to a flask for further experiment. 



Tartrate of ammonia was prepared by neutralizing a tartaric-acid solution 

 with aqueous ammonia ; this was mixed with phosphate-of-soda solution, 

 made by dissolving carefully washed crystals of the salt in hot distilled 

 water. The mixture containing about 5 per cent, of the two salts was 



