126 



BACTERIA IN RELATION TO PLANT DISEASES. 



is good, but when it is feeble or when the steam pressure is high the water becomes 

 too hot and steam sometimes escapes into the reservoir. The water therefore must 

 be hurried through the tank by the use of a steam pump, or else less steam must 

 be allowed to enter the copper pipe. If the writer were to build another similar 

 apparatus he would make the condensing tank 2 feet higher and add 10 feet to the 

 length of the coil of tin pipe. The condensing tank is provided at the bottom 

 with a i -inch inflow pipe for the cold water (it should be i i/J-inch), and at the top 



with a i^-inch outflow pipe (it should 

 be 2-inch), for the exit of the wanned 

 water. There is also a i-inch flush 

 pipe at the bottom for the occasional 

 removal of sediment. 



The size of the outflow pipe, which 

 must be somewhat larger than the in- 

 flow pipe, prevents any possibility of 

 clogging and overflow. All the metal 

 parts which come into contact with the 

 distilled water are tinned or nickel- 

 plated. Connected with the lower end 

 of the block-tin coil (by tin solder, 

 which must not contain lead or zinc) 

 is a smaller (i^-inch) block-tin pipe 

 (i i), which leads the distilled water into 

 (15) the storage tank (3 4 -inch pipe 

 would be better, and without any joint). 

 The reservoir in this case is a white- 

 enameled bath-tub, on the top of which 

 is clamped down a cover of thin sheet 

 copper ('(,- inch), the inner face of 

 which has been carefully tinned. Plate 

 glass ground to fit would be better, and 

 the tub itself is likely to be discarded 

 in the near future, i. e., when some 

 more satisfactory storage tank can be 

 found. The problem of the proper 

 storage of distilled water in quantity is 

 the hardest one, the solvent power of the 



r ig. 118.* 



water is so great. From the bottom of 



this bath-tub several hundred feet of i^-inch block-tin piping lead to various rooms 

 in the building. In addition to the terminal faucets there is a general cut-off just 

 above 18, which is necessary in case of an accident to any faucet or part of the 

 piping. There is also an overflow pipe (17), which does not enter the sewer, but 



*Fic. nS.^Early stage of stomatal infection in angular leaf-spot of Rivers cotton. Hothouse 

 infection produced by spraying Bacterium malvacearum upon the surface of the leaves. For a much 

 later stage see fig. 80. 



