Sound 

 ings, 



208 HYDROGRAPHICAL SURVEYING [chap. viii. 



Necessity The soundings mii6t be put into the book to the exact 

 Fractions ^^P^^ obtained, but it will depend upon the scale, the general 

 accuracy of the chart, and the thickness of the soundings, 

 how far halves and quarters will be placed on the sheet. As 

 a rule, fractions should be retained up to 6 fathoms; and over 

 that depth only the even fathom, taking, of course, the fathom 

 under the depth. Thus a sounding which, when reduced to 

 low-water, is 9|, will appear as 9 fathoms. 

 Reducing The necessity for accuracy in reducing soundings to Ioav- 

 water will also very much depend on the scale of the chart and 

 the depths. It is evident that with soundings of over 6 fathoms 

 at low-water, if we are using a small scale, where the size of 

 the figure placed on the chart will, in reality, cover ground 

 on which we have taken five or six soundings, any nicety of 

 reduction is an absurdity, and labour thrown away ; but in 

 shalloiv water the reduction will be just as necessary in a small 

 scale as a large, as a sounding of 5 fathoms will be a danger 

 or not, according to Avhat amount of reduction we apply. 

 Calling It is usual in surveying vessels to depart from the time- 



Sound- honoured habit of calling soundings, and to call simply " Six 

 and three-quarters," " Five and a half," and so on. This is 

 simpler, and saves time. The men should also be trained to 

 call out sharply, and on no account allowed to drawl. 



There are, however, two exceptions to this. " Seven " and 

 " Eleven " have a great similarity when called from the chains, 

 and to prevent mistakes " Deep eleven " should be called. 

 Similarly, " Nine " and " Five " sound much alike, and " Deep 

 nine " should be given. " Five " and " Seven " are given 

 simply. 

 "Shoal On all occasions, whether in ship or boats, when the leads- 



Water." man suddenly gets a shoaler cast than expected from his 

 previous soundings, he should call out " Shoal water," without 

 waiting to complete his usually fruitless endeavours to gather 

 in the slack line and find out the depth. The author has 

 been on shore from the neglect of tliis, the leadsman being 

 fooUsh enough to wait until he had repeated his cast, so as to 

 give the correct depth, and gave no warning to the officer on 

 the bridge until too late. 



Belcher proposes a plan for ascertaining the depth on a bar 

 which it is desired to cross, wdthout risking a capsize, which 



