4 



oysters were spread all over a given area, or grew in clusters of large or small size, or were scat- 

 tered singly or iu small groups. 



3. The determination of the temperatures of the surface and bottom water at each locality 

 and the velocities of the currents. 



4. The preservation of specimens of oysters of different ages, from each locality, and speci- 

 mens of the bottom and bottom water. 



5. The determination of the existence of any deposit of mud or other earthy or vegetable 

 material and the determination of the character of the bottom beneath the oyster beds. 



(>. The determination of the source of the sediment if any was deposited and the means of 

 directing it, if injurious, away from the lieds. Also to determine whether ice ever rested on the 

 beds and so destroyed them. 



7. The determination of the density of the water, with special reference to the question of dis- 

 placement of the salt water by the fresh water from adjacent streams and rivers. 



The Superintendent also desired that the examination should, at first, be confined to a limited 

 area and made exhaustive. Subsequently the investigation was to be extended as far as the means 

 at the disposal of the Survey would permit. 



The instructions were received on the 3d August, 1878. On the 7th of that month the vessel 

 sailed from Baltimore, Md., to execute them, and the party remained actively in the field until the 

 15th October, when the season closed. As the investigation was novel in design and execution, 

 and as the difficulties encountered by the party were mainly due to the absence of all experience 

 and previous exertions in the same held, 1 have thought it best to preface the account of the results 

 of our labors by a short description of the methods employed iu making the several determinations 

 required by my instructions. 



METHOD OF CONDUCTING THE INVESTIGATION. 



The examination of the different beds was carried on in the following manner: 



1. — Delineation of the beds. 



The services of an oysterman of experience, and who was well acquainted with the localities 

 of the different beds, was first obtained; the vessel was then anchored in such a position as to 

 enable- her use as one of the points for angling upon, and her position carefully fixed by sextant 

 angles upon all points recognizable upon the chart. At the same time angles were taken upon any 

 object that might be useful subsequently in fixing positions, either of the boats or schooner. By 

 carrying forward our own points in that manner it was possible to dispense with signals, the 

 erection of which would have occasioned much delay and the sacrifice of time and labor, to procure 

 y an unnecessary degree of accuracy. The boats then ran traverse lines, more or less open, over 

 the adjacent beds, the size of the interior angle and the length of the line depending upon the 

 supposed size and character of the bed; our general method was to work with the tide and endeavor 

 to cross the lines as we returned over the ground. The "oyster pilot" was sent in one boat and 

 one of the ship's company, who was an old oysterman, was sent in the other. They were provided 

 with poles, which were marked to feet, and continually probed and examined the bottom as the 

 boat passed over the line. The depth of water and character of the bottom were recorded as in 

 ordinary hydrographic surveys. The position of the boat was frequently ascertained by sextant 

 angles, but as the "points" were not always well defined, two angles were not considered sufficient, 

 and angles on all prominent objects were taken. Occasionally, when in proximity to the schooner, 

 mast-head angles and bearings were used for ascertaining the position of the boat, and in a few 

 cases the bearing and distance of some well-defined point of land was estimated. 



At intervals the boat was anchored, her position fixed, and specimens of oysters, bottom, and 

 water obtained, and the temperature of the air, and surface and bottom water, observed; the 

 character of the substratum of the bottom was also noted, and the set and velocity of the current 

 recorded. The observations for ascertaining the character of the bottom beneath the surface and 

 those for temperature were more frequently made than the others, and the current was measured 

 only at such points as would give a fair idea of the general set of the flood and ebb tides; but 



