REPORT OF COMMISSIONER OF FISH AND FISHERIES. 95 



found that egjjs, representative of the sliad and wbitefisli, could be 

 closely imitated in roundness, size, and transparency. Those intended 

 to represent smaller eggs, as of the Spanish mackerel and codfish, were 

 jirodaced by pouring melted resin through sieves from an elevation, the 

 fiilling i^articles being caught in water. The latter class had to be 

 screened to separate the different sizes, those made by means of tubes 

 being practically uniform. During some months attention was paid 

 almost wholly to the selection of substances which could be united to 

 produce a composition of required specific gravity for eggs semi-buoyant 

 and floating. Meantime the point of obtaining eggs of perfect round- 

 ness was solved, and while yet looking to the regulation of the specific 

 gravity it was accidentally found that eggs of resin could be made to 

 represent any desired specific gravity by subjecting them to solutions 

 of salt water of relative densities. When this was ascertained it was 

 readily seen that both kinds were possible from the same material, the 

 brine for the semi-buoyant ones requiring to be weaker and for the 

 floating ones stronger. 



Another duty devolving upon the superintendent was that of assist- 

 ing the Commissioner in preparing for and carrying out exx)eriments 

 for determining the relative value of artificial salt water as the basis 

 of maintaining an exhibit of marine animals and plants at the Colum- 

 bian Exposition. As it was impracticable to devise satisfactory means 

 for circulating the small quantity of water with which he was experi- 

 menting, it was necessary to adopt the alternative of oxygenizing the 

 water by means of air circulation. As long ago as October, 1888, while 

 the Ohio Valley Exposition at Cincinnati was occupying attention, 

 instructions were received from the Commissioner to establish a small 

 number of aquaria in the west end of the building and provide therefor 

 au air circulation. Attempts were then made to liberate air through 

 rubber tubing gashed with a knife or perforated with i)in holes, but 

 without good results. Following this, tests were made with sections 

 of grapevine and other twigs selected from the mass of driftwood found 

 on the shores of the Potomac at the shad-egg station. Grapevine 

 gave tolerably fair results, but in time it was discarded, and Mr. W. P. 

 Seal, then in charge of the aquaria, adopted sponge, a crude alternative, 

 which, being cut into small pieces, was thrust 'into holes punched into 

 half-inch rubber tubing. 



All former efforts to diffuse volumes of air through water in currents 

 sufficiently minute to effect ideal aeration having failed, and the solu- 

 tion of the problem being dependent upon the aj)plication of air circu- 

 lation, active steps were taken to discover a material of the desired 

 porosity. Plugs were made in cross-section from various kinds of wood, 

 with the hoj)e of finding one of suitable i)orosity. Mr. L. G. Harron 

 removed a dead branch from an American linden tree on the public 

 Mall, and it was just what was desired. From that day the question of 

 successful liberation of air in water, for our purposes, has been solved. 



