BULLETIN OF THE UNITED STATES FISH COMMISSION. 



99 



repairing, by a simple but far more expensive air-pump, A, which con- 

 sists of a metal vessel in the shape of a broad cylinder, with a leather 

 lid or valve, the piston of which can 

 be moved up and down with the 

 hand. At the first pressure the 

 tube is emptied and air enters into 

 it, which at the second pressure 

 enters the water through the open- 

 ings in the tube, &c. At B there 

 is a tin ice-box, which should 

 not have any sharp edges, against 

 which the fish might hurt them- 

 selves. Fig. 2. 



As regards fresh- water fish, it maybe laid down as a general rule 

 that they will keep best when transported in water of the lowest possi- 

 ble temperature. The colder the water the more oxygen will it absorb, 

 whilst the quantity of oxygen consumed by the fish will decrease in pro- 

 portion as the temperature gets lower. The lowering of the temperature, 

 therefore, offers a twofold advantage, and the use of ice cannot, conse- 

 quently, be too strongly recommended. To avoid any violent concus- 

 sions, which might hurt the fish, the barrel may be placed on springs, as 

 was shown in a transporting vessel from Velp, Holland. 



Of the different methods of introducing air I prefer the one where air 

 is introduced through tubes by means of an air-pump or bellows, because 

 thereby the hurtful carbonic acid formed by the breathing process of 

 the fish is more thoroughly expelled, and the vessel can be entirely filled 

 with water. Beating or lashing the water is always injurious to the fish. 



As long as specially-constructed railroad cars for transporting live 

 fish are not provided, persons who ship live fish will have to resort to 

 various more or less satisfactory means of transportation. For the 

 use of the Berlin Aquarium I have constructed an apparatus which I 

 consider as specially suited for transporting fish a considerable distance. 

 It was exhibited under No. 514. It had been my object to meet the fol- 

 lowing conditions, which have to be considered more or less in transport- 

 ing fish : 1, to provide sufficient air for the water; 2, to keep the water 

 free from slime and other impurities; 3, to maintain a suitable temper- 

 ature; 4, to prevent the beating or shaking of the water, and thus to 

 protect the fish from injuries. Fish with broken scales or fins will not 

 keep well. 



This object I have reached in the following manner by connecting 

 three vessels: 



From the transporting vessel proper, No. 1 (see Figs. 3 and 4), as 

 much water flows into vessel No. 2, on the same level, as is introduced 

 from the raised vessel No. 3. Through the spigot d the water flows into 

 an air-tight rubber tube connected therewith, which empties at the bot- 

 tom of the vessel, or near it, at the place marked F, which is as far re- 



