38 



SCIENCE. 



[N. S. Vol. XVIII. No. 445. 



of the other governineut surveys concerned, 

 their results are all being placed at the dis- 

 posal of this bureau for the purpose of 

 including- them in a general adjustment by 

 which a homogeneous system of vertical co- 

 ordinates for the whole country can be 

 established which shall stand side by side 

 ■with geographical coordinates before re- 

 ferred to. 



THE DATA FOR A CHART. 



The geodetic functions of the survey 

 have been dwelt upon in this address at 

 some length because their precise nature 

 and great usefulness are not commonly un- 

 derstood, but the administration of the sur- 

 vey has always remembered that the survey 

 owes its existence to the urgent need for 

 reliable charts of the coasts. Their im- 

 portance to commerce is apparent. The 

 vast sums which every civilized nation is 

 expending in improving its facilities for 

 commercial intercourse are sufficient evi- 

 dence that everything which can be done 

 to promote the safety of navigation must 

 be done. Every civilized nation also rec- 

 ognizes the fact that this is a duty which 

 it owes not only to its own citizens, but to 

 the world. As an evidence of this con- 

 sider the lighthouses which flash their 

 friendly warnings or g-uiding welcome to 

 ships in all parts of the world, the buoys 

 which mark dangers along channels, the 

 sounding sirens which cry their caution 

 through the fogs, the storm signals which 

 are displayed, the sturdy life-savers who 

 patrol the coasts and the guiding charts 

 with which this survey is mainly concerned. 



On the open ocean the chart has its least 

 value, for the dangers to which the mariner 

 is there exposed are not such as can be 

 remedied by a chart. Storms, fogs and 

 collision with other ships in the lanes of 

 travel are dangers to be apprehended, but 

 the kaowledge that there is deep water un- 

 der the keel of the ship is a source of com- 



fort to the mariner, however risky it may 

 appear to the landsman. The story of the 

 darky who compared the dangers of a sea 

 voyage with the safety of railway travel is 

 familiar to all: "If the ship sinks whar is 

 yo, but if the train gits smashed dar yo 

 is," illustrates one point of view, but that 

 of the sailor is told in rhyme which the 

 refined muse of the Worcester Polytechnic 

 may not Imow and is therefore cited here: 



Foolhardy chaps as lives in towns, 

 What danger they are all in. 



And now lie quaking in their beds 

 For fear the roof should fall in. 



Poor creatures, how they en^■ies us, 



And wishes, I've a notion, 

 For our good luck, on such a night 



To be upon the ocean. 



While you and I, Bill, on the deck 



Are comfortably lying, 

 My eyes! what tiles and chimney-pots 



About their heads are flying. 



But when the ship nears the coast a bur- 

 den of great responsibility rests upon the 

 navigator, for on his skill, experience and 

 knowledge the safety of life and property 

 entrusted to his care depends. He turns 

 to the chart and follows the path marked 

 out for him by the skill of the surveyor. 

 When the depth of water is great as com- 

 pared with the draft of vessels, the prob- 

 lem of the hydrographer is comparatively 

 simple, but where it decreases so as to ex- 

 ceed not very much the draft of vessels, the 

 problem of finding every hidden rock, every 

 coral pinnacle or shoal, requires an im- 

 mense amount of work and minute accuracy 

 in the soundings and locations. Imagine 

 to yourselves a totally submerged city and 

 solve the problem of finding every chimney, 

 every steeple, every house top and every 

 street by means of a sounding lead, and 

 you will have a good illustration, even 

 though it be a slightly exaggerated one, 



