TROPICAL AQUARIUM FISHES 113 
tioned, iron is the least injurious and zinc the most, on account of the 
rapidity of chemical action of salt on this metal. Therefore, galvanized 
iron is to be particularly avoided, as it is zinc-plated. The author on one 
occasion could only secure a galvanized pail in which to bring a collection 
home. As the trip was only three hours and the pail was a well-seasoned 
one he thought the chances of success were reasonably good. When the 
can was opened the water showed a slight milkiness and the fishes were 
nearly dead, although they had not been crowded. On being placed in the 
aquarium they soon revived. The best metal in which to ship is tin. This, 
or any other metal, should first receive a coating of asphaltum varnish. 
Even galvanized iron when asphaltum-coated is safe for journeys of 
moderate length, but the asphaltum will eventually chip off and the pail 
or can should be carefully looked over each time before using. It might 
be well to say here that the life of tin pails for freshwater will last much 
longer if coated with asphaltum varnish. A thin coat spread evenly lasts 
better than a thick one. 
The very best water-shipping medium is a protected glass bottle or 
carboy. Arrangements can usually be made to rent or borrow a few of 
these from drinking-water concerns. If possible the water should be 
taken from several miles out at sea and not near the mouth of any large 
river, Clear seawater may be stored indefinitely in carboys in a subdued 
light, although it would be better to first filter it to remove the larger 
microscopic life. 
Artificial Seawater. Experience varies regarding the use of artificial 
seawater. This may be due to difference in the degree of purity of chem- 
icals used or care in their mixing. The author has not been particularly 
successful with artificial marine water, although some writers claim it to 
be better than ocean water because of its freedom from impurities and 
marine bacteria. The following is a correct working formula for artificial 
seawater. There are other elements in the ocean, but in such small quanti- 
ties as to be negligible for our purposes: 
Sodium chloride (Tablesalt)..2 Ib. 8 25. 18 gr. 
Magnesium chloride ........ 35. 53. 13 gr. 
Magnesium sulphate ........ 25. 33.19 8 gr. 
Potassium sulphate ......... 55. 29 10 gr. 
and sufficient wellwater to bring the whole to ten gallons. 
These proportions of salts, expressed in the Metric system, would be: 
Soditim, chloride 2... 01.6: cee eds 663 grams. 
Magnesium chloride ...........---+-++55 75 
Magnesium sulphate ..........--.-+-455- 50 “ 
Potassium sulphate .............00-00 ee Loe 
Added to 25 litres of wellwater. 
