126 



THE POPULAR SCIENCE MONTHLY. 



constitutes, as is superficially said, a toxic 

 element. The phenomenon is more com- 

 plex. The organic matter in suspension or 

 in solution creates in the water a peculiar 

 medium, suitable for the development of 

 exceedingly small beings of the genus Vibrio. 

 It is no longer mere water it is a world of 

 microscopic animals and plants which are 

 born, live, and increase with bewildering 

 rapidity. The infusoria find in the water cal- 

 careous, magnesian, and ammoniacal salts, 

 and their maintenance is thus secure. Drink 

 a drop of this liquid, and you swallow mill- 

 ions of minute beings. But there are vib- 

 rios and vibrios. There are those which 

 are capable of setting up putrefaction in 

 our tissues. These are our enemies, often 

 our mortal enemies. Let water be placed 

 in contact with organic remains capable of 

 nourishing these malignant vibrios, and it 

 at once becomes more dangerous than any 

 poison." 



A Motherly Fish. There is found, in the 

 clear, pebbly streams which descend to the 

 plains from the mountain-ranges of Trini- 

 dad, a small fish of the perch tribe, which 

 in its great care for its young presents a 

 singular contrast to all other known fishes. 

 A writer in Nature states that on one occa- 

 sion, as he approached the water for the 

 purpose of takiug his morning bath, his at- 

 tention was attracted by the eccentric move- 

 ments of one of these little fishes. In gen- 

 eral they are very shy, scudding off into 

 deep water on the approach of man ; now, 

 however, when a hand was put into the 

 water, the fish darted forward again and 

 again, striking the hand with considerable 

 force. The explanation of this conduct was 

 soon found : in a small hollow near by, 

 about the size of half an egg, artistically 

 excavated in the bright quartz-sand, a multi- 

 tude of tiny fish were seen huddled together. 

 They had apparently been very recently 

 hatched, and were no larger than common 

 house-flies ; the parent-fish kept jealous 

 watch over her progeny, resenting every at- 

 tempt to touch them. Returning to the 

 same spot on the following day, the writer 

 of this narrative searched there in vain for 

 the fish and her young. At length, how- 

 ever, a few yards farther up stream the par- 

 ent was discovered guarding her fry with 



zealous care in a cavity similarly scooped 

 out in the coarse sand ; any attempt to in- 

 troduce one's finger into the nest was vigor- 

 ously opposed by the watchful mother. 



Arsenical Colors. A Swedish chemist, 

 Dr. Hamberg, has made some important re- 

 searches on the arsenical coloring-matters 

 of wall-paper. The paper of the room in 

 which the experiments were conducted had 

 a light-green ground, with an ornamental 

 pattern of brownish-yellow color ; this yel- 

 low was probably derived from an ochre, 

 but the green resembled Schweinfurt green, 

 and was strongly arsenical. An arrange- 

 ment was made for drawing a current of 

 air through a series of U-shaped and bulbed 

 tubes, suspended on the wall. The pas- 

 sage of air was continued from July 16th 

 to August 16th, and it was calculated that 

 during this time about 2,160,000 cubic 

 centimetres of air had traversed the sys- 

 tem of tubes. Some of the tubes had been 

 plugged with cotton-wool, while others con- 

 tained a solution of nitrate of silver, and 

 at the termination of the experiment the 

 contents of the tubes were separately ex- 

 amined. The results showed that there had 

 been an arsenical exhalation. The fam- 

 ily living in the house had never suffered 

 any marked injury from breathing this I 

 poisoned air ; but Dr. Hamberg, after sleep- 

 ing in a room by the side of the apartment 

 in which his experiments were made, and 

 with the door open, frequently experienced, 

 on the following morning, a sense of heavi- 

 ness in the head, and a general feeling of 

 weariness. 



Distribution of Water in Aquaria. In 



constructing aquaria it is important to bear 

 in mind the fact that, for aquatic animals 

 which breathe without lungs, the value of 

 water does not depend so much on its 

 amount, as upon its distribution in such a 

 manner that it may be sufiiciently oxygen- 

 ated by contact with the atmosphere. Mr. 

 W. A. Lloyd, who calls attention to this 

 matter in the Zoologist., says that when the 

 amount of surface of water exposed to air, 

 as well as the actual quantity of water, is 

 regulated according to the known require- 

 ments of the animals to be kept, the well- 

 being of the creatures is promoted, and the 



