DISTILLED WATER. 125 
The following description and figure of a distilled-water apparatus devised by 
the author for use in the Laboratory of Plant Pathology, United States Department 
of Agriculture, may be of interest, therefore, to some. The apparatus consists of a 
galvanized-iron boiler similar to those used in kitchen ranges. It is 18 inches in 
diameter and about 5 feet high. The top is sawed off and to it is bolted a stout 
iron ring with a flange, on which rests a 4%-inch brass cover. In the lower half of 
this boiler is a coil of 52 feet of inch copper pipe, the upper end bent downward 
and securely fastened in the bottom of the boiler to a steam pipe (1 inch) connected 
with a 14-inch steam pipe leading to the ordinary steam boiler in the engine room 
in the basement; the lower end connected with an iron steam pipe (1 inch) leading 
to a steam trap (Mark traps are said to be the best). Around this copper steam 
pipe, which is of course tin- 
plated, stands the river water 
which is to be converted into 
steam by contact with the hot 
pipe. This hydrant water is 
kept always at about the same 
level (level of fig. 5 in plate 14), 
by means of a tinned-copper ball 
float (automatic cut-off) which 
closes the mouth of the inflow 
pipe when the water rises be- 
yond a certain point. The upper 
part of the cylinder is a steam 
chamber under very moderate 
pressure (0 to % pound, rarely 
more). ‘The excess of pressure 
is dissipated either by escape of 
steam through the safety valve 
(9), which is not weighted, or 
through the coil of pipe in the 
condenser. The steam passes 
from a securely riveted tin-lined 
copper catch basin (8) into a 34-inch block-tin pipe (10), which is fastened to a 
tubular projection from the catch basin by means of a collar screw. The tubular 
projection from the top of the catch basin is soldered in place and also held by a 
flange inside the copper top, so that it can not be forced out by any attainable 
degree of steam pressure. The 34-inch block-tin pipe passes to the room above, 
where it is coiled for a length of 35 feet inside a tin-lined copper tank resting on 
the floor. ‘The height of the condensing tank is 18 inches and its diameter is the 
same. When in operation this tank is full of running water. ‘Theoretically, this 
condensation tank is large enough, and it is so practically when the hydrant pressure 
*Fic. 117.—Detail from fig. 115 at B, showing an early stage of water-pore infection of cabbage. 
The bacteria have not yet entered the spiral vessels. The large dark bodies are nuclei. 
