USE OF U-BOATS

Gisborne Herald, Volume LXVI, Issue 20108, 30 November 1939, Page 3

USE OF U-BOATS

LAYING MINEFIELDS SHIPS OF NEW CLASS ACTIVITIES BY NIGHT LONDON, Nov. 28. Naval officers believe that the minefields in which the Simon Bolivar, 8.0. Borjesson. Blackhill and Grazia were destroyed must have been laid at night by German submarine minelayers—probably by two working together to make the field larger. It is known that a new class of submarine minelayer, of about 1100 tons, was being built In Germany last summer, and that at least two were nearly complete. Vessels of this size would carry at least 48 mines each, which could be laid any distance apart, and not necessarily in straight rr ws Zig-Zag Pattern Favoured Many fields in enemy waters are laid in zig-zag patterns, for the purpose of making mine-sweeping more difficult and more dangerous, and also for ensuring that no surface ship passes unharmed between two wide-ly-spaced rows. The fact that the Simon Bolivar hit two mines is taken to indicate that this field was laid on the zig-zag plan. As she drifted helpless after the first explosion, she touched another mine in the zig-zag pattern. This method of sowing is practised only in enemy waters because it is impossible to piot the exact positions of the zig-zagged mines on the secret charts issued to commanding officers. The fact that the disaster to the Simon Bolivar occurred in a channel that ! s regularly swept is not considered as implying any slackness by the mine-sweepers. It is a favourite trick of German U-boat minelayers to approach at periscope depth the area that is being swept and there watch the courses steered by the sweepers. Release bv Chemical Action Those courses are followed by the minelayer, either at some distance behind or after nightfall, and the mines are sown in waters that will be reported t.o the British Admiralty as having been swept. This practice endangered convoys in the last war. Possibly the mines were laid at a considerable depth, and automatically released after a certain time by the chemical action of sea water.