100 MADRAS FISHERIES BULLETIN VOL. XIII, 



consumer chose to neglect the suspicions caused by the condition 

 of the canned contents. On the other hand (see below s.v. 

 'springers,' paragraphs 136—139) the consumer should be sure 

 that the can is really a 'swell' ('blown' by reason of decom- 

 position) and not merely a slightly distorted one or 'springer. ' 



133. Defects in empty ea/is before packing. — These mainly arise 

 from defective soldering or seaming of the can bodies and 

 bottoms. In U.S.A. practice, cans made by can- making factories 

 whose sole or main business is the production of empties for the 

 use of the canning factories, have arrived at such perfection, 

 especially in the nearly solderless or sanitary lock-seam cans, 

 that 2 per mille is the maximum allowed for defective cans and 

 the manufacturer makes good any losses due to any excess over 

 such proportion. But the cans mostly in use and of that make 

 are the cylindrical cans so well known as containers of salmon, 

 soups, preserved fruits, vegetables, etc., and not only are these 

 easy to make by automatic and very perfect machines but they 

 can be and are regularly tested for complete air-tightness before 

 leaving the can-making factory. There are various devices for 

 the purpose, but compressed air is the more general and simple 

 method, by which cans are submitted, under water, to jets of 

 compressed air which instantly issues in a stream of bubbles from 

 the smallest aperture. Water under pressure is also but less 

 commonly used. But owing to the perfection of modern lock-seam 

 plant the testing of empties is of less importance than formerly. 



134. In India some such device is advisable, for experience, as 

 gained by compelling solderers to place their marks on can bodies 

 when making empties, shows that leaks are nearly as common in 

 making the cans as in sealing them after packing. It is however 

 difficult to test such cans as shallow, rectangular quarters. A 

 shallow flat bottomed pan of water with a jet in the centre convey- 

 ing compressed air admitted by a conveniently placed tap worked 

 by hand or foot to an empty can held firmly below the water, is 

 perfectly feasible, and might save its cost in a year or two from 

 the diminution of leaks and consequent spoils. 



This source of trouble is of course absent altogether in 'solid 

 drawn ' cans as made (quarters and ovals) in the Beypore factory, 

 since there is no joint or seam whatever in the empty bodies. 



135. Defects from leaks after packing and sealing. — These have 

 been sufficiently dealt with elsewhere in describing the several 



