44 Dv Davy on the Specific Gravity of the Water 



Antigua^ towards the end of an unusually dry season ; the 

 lowest that of 102G0, was of water from near the shore of 

 Barbadoes, taken up after a good deal of rain had fallen dur- 

 ing the preceding three months. 



With the exception of Nos. 6 and 7, there is a regular 

 and well iTiai'ked increase of the specific gravity of the water 

 with the increasing distance from the land. In these two in- 

 stances, it is probable that the slight diminution in the one, 

 and the no augmentation in the other, compared witli the 

 preceding No. 5, may have been owing to some heavy 

 showers of rain which fell on that part of the sea, about the 

 time that the steamer was passing. 



For practical purposes in navigation, no doubt, it is desir- 

 able that more numerous observations should be made on the 

 specific gravity of the water off the coast of British Guiana, 

 and witli all possible accuracy as to intervals of distance, 

 position and distance, from the shore. Should it be found, 

 that in all seasons there is a certain and partly regular 

 diminution of the specific gravity of the water in nearing 

 the coast, may not the circumstance be turned to use- 

 ful account, especially by the mail steamer ? Provided 

 with a hydrometer, even in the darkest night, aided by 

 soundings, it is probable the position of the vessel might 

 be determined Avith accuracy within the range of a very 

 few miles, so as not to be under the necessity of lying 

 to, pei'haps sixty miles from land, as is now often the 

 case, and even in nights not particularly dark, — a necessity 

 connected with the lowness of the coast-line of this vast 

 alluvial district, there being on it no conspicuous land-mark, 

 and even the light of the lighthouse in George Town being 

 often obscured by mist. 



Reflecting on the subject, it naturally occurs to one, whether 

 the hydi-ometer might not be useful to navigators, not only 

 in making land where the well-known coast is at all similar 

 to that of British Guiana, as regards rivers and lowness, but 

 also in exploring expeditions off unknown coasts, where the 

 existence of rivers is uncertain, and they are anxiously sought 

 for. In reading the accounts which we hear of the surveys 

 of the coast of New Holland, I have fancied that bad a hydro- 



