I04 CHALLENGER 



and men found themselves away in the whaler, sounding under 

 sail with lead and line, to augment the work of the echo sounding 

 launches. Such methods of sounding had probably not been prac- 

 tised for over 40 years, but as long as results were accurate Jenks 

 cared nothing for appearances or discomfort. 



The channel as far as Culmore, where it enters the river, skirts 

 the north shore of the lough, and passes within a few hundred 

 yards of the Eire shore in some places. Although main triangula- 

 tion stations were recovered on the south shore of the lough on 

 which basis the survey was built up, it was still necessary to 

 include some fixed points along the Eire shore. Theodolite parties 

 who landed on this coast were nervously looking over their 

 shoulders and expecting to be interned at any moment, but when 

 a Civic Guard did eventually appear he was only interested in 

 discussing the progress of 'our' war with the English surveyors. 



Once the survey entered the river the scale was greatly in- 

 creased. The reason for this was unknown to those in Challenger 

 at the time ; it was only later, when the large United States Base 

 and fuelling wharves for their escort vessels were built at Lisa- 

 hally on the south bank of the river, that it became clear why this 

 survey had been ordered by the Hydrographer in the early part 

 of 1 941. 



By early May the Londonderry surveys were complete and the 

 ship was in Lough Lame, for this too was to play its part as an 

 anchorage for escort vessels employed in the Atlantic battle. The 

 officers and men of Challenger had now served together for some 

 considerable time and many had served under Commander Jenks 

 in Iceland ; by now they were well practised in the arts of rapid 

 wartime surveying and quicker results were being obtained as each 

 new survey was taken in hand. But at Lame there was considerable 

 trouble with the triangulation in the upper part of the lough : 

 the triangles observed between the stations which had been erec- 

 ted along both shores refused to close within reasonable limits 

 of 180 degrees. At low water this part of the lough is composed 

 of acres of mudbanks through which winds a narrow boat channel, 

 and across these soft flats it was necessary to walk to reach the 

 triangulation stations on the foreshore. After two or three muddy 

 surveyors had returned with angles which did not add up to the 



