146 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



were in two sizes, all rectangular in shape, the smaller (24 in number) with a frontage 

 of 5i feet and a width from before backwards of 3f feet at bottom and 5 J feet at top ; 

 the larger size (10 in number) of twice the above length, but of the same dimensions 

 otherwise. The inner tanks were in three sizes, the 8 smallest with a frontage of lf> 

 leet outside and 11£ inside, the next (a single tank) of double these dimensions, and 

 the third (likewise a single tank) 56 feet long on the middle line, with glass frontage 

 of 60 feet and 40 feet linear, on the outer and inner faces respectively. All the tanks 

 of the inner circle were 8f feet from front to back. 



The fresh water was derived from Lake Michigan through the general water supply 

 of the park and passed through pressure niters* of a nominal capacity of about 10,000 

 gallons an hour, but sometimes worked by us at three times this rate. In order to 

 secure the perfect clearness of water indispensable to a proper display of our material 

 it was found necessary to introduce an alum tank into the circulation, provided with 

 an automatic regulator by which a fixed proportion of alum in solution was mingled 

 with the water before it passed through the filters. The flocculent precipitate thus 

 formed by the union of the alum with the mineral matters of the lake water so entangled 

 all minute suspended particles that they were taken out by the fine quartz sand of the 

 filters, leaving the water beautifully clear and also chemically free from any surplus 

 of alum. Provisions were likewise made for warming this water, when necessary, 

 after it emerged from the filters, by passing it through a coil of brass tubing encased 

 in a large piece of heavy iron pipe filled with steam from the boiler used in heating 

 the building. 



A receiving pool, in three divisions, was made in the lagoon by inclosing and sub- 

 dividing an area along shore, adjacent to the aquarium, with a fence of wire netting 

 fastened to heavy wooden posts. As the water level varied greatly with the direction 

 of the wind, a seine with numerous floats was attached to the upper border of this 

 fence. The extremely unfavorable character of the weather early in the season pre- 

 vented the rapid accumulation of large quantities of specimens for which we had 

 planned and prepared, and this pool was consequently but little used. But for this 

 unforeseen and unavoidable delay we should have escaped many of the subsequent 

 difficulties of aquarium maintenance. It was a part of our original plan to store our 

 field fresh- water collections — especially those brought from considerable distances — 

 in this pool, leaving them there until those injured in transit or diseased had either 

 died or recovered, selecting then from the remainder, from time to time, what were 

 needed for the aquaria. Pressure of time and a determination to be "ready May 1" 

 usually compelled us to add the fresh material to the exhibit as fast as it came in. 



The first installment of salt water — to the amount of 42,000 gallons — was trans- 

 ported from the sea at Beaufort, N. C, in seven tank cars loaned to the Commission 

 by the Standard Oil Company, and hauled by the Chesapeake and Ohio Railroad 

 free of charge. The saltwater circulating system t consisted of an underground 

 cistern 46f feet long, 18if feet wide, and 8.4 feet deep, a pressure tank in the roof of 

 the main Fisheries Building 30^ feet in circumference and 5 feet deep, supply pipes 

 of hard rubber leading from the latter tank to the aquaria, return pipes of the same 



* Furnished, put in place, and maintained gratuitously by the (). H. .Jewell Filter Company, of 

 Chicago. 



t A technical description of the circulating plant of the aquarium, prepared by Passed Assistant 

 Engineer 1. S. K. Reeves, chief engineer of the Commission, is appended to this article. 



