128 PACIFIC SALMON FISHERIES. 
hausters, in which the cans travel along a spiral, are also in use. — 
By this means the contents of the can are heated and the greater — 
part of the air exhausted, which is the object of the first cooking in 
the retort under the method formerly in general use. 
A recent invention, which the inventor claims will do away with 
the steam exhaust box, and thus save a large amount of valuable — 
floor space in the canning “‘line,”’ is the power vacuum pump, known 
as vacuum exhausting machine, by means of which air is exhausted 
from the cans, accomplishing the same purpose as the steam exhaust 
box. Some of these machines have been in active use for several 
seasons, with most satisfactory results. 
Leaving the exhauster the cans pass to the double seamer, which 
fastens the cover on tightly with a double seam or crimp. It should 
be stated that no solder is used in attaching the top on the can, the 
curled flanges of the cover being coated around the outer edge with 
cement or other sealing fluid to take its place. Solder, however, is 
used in joining the side seam of the can, this being done when the can 
is manufactured. The cans then leave the machine on an endless 
conveyer and pass to the men who transfer them to the coolers, and 
these are immediately placed upon the trucks and run into the retort 
for the one cooking they are to receive. The time they are to remain 
here is somewhat variable, 70 to 125 minutes with a tomperatare of 
242° F. being the common period. 
By the use of these cans the soldering machine is done away with. 
It also does away with the first cooking and the subsequent venting 
and soldering, a saving both in labor and time consumed. 
REPAIRING CANS. 
Imperfect cans which are repaired before the first cooking are 
naturally in the same condition as if there had been no defects. If 
the leaks are discovered after cooking and are repaired at once and 
the contents recooked, they are still very good, the only difficulty 
being that by blowing or venting them a second time they lose weight. 
The above goods usually go in with the regular pack of their kind 
and are not classed as regular ‘‘do-overs.”’ 
When, however, a cannery is running at full capacity, defective 
cans can not always be repaired and recooked at once and are some- 
times set aside for days. Decomposition follows, of course, as with 
any other meat that is exposed to the air, and the fish becomes unfit — 
for food. When recooked the meat becomes mushy and the blowing 
or venting makes the cans very light, a defect which is frequently 
corrected by adding salt water. This, the ‘‘do-over,” is the lowest 
class of goods. In the old days, and even yet to some extent, such 
cans are sold without labels to brokers, or else are given some indefi- 
nite label, and sold in the lumber, mining, or negro districts, or 
