June 17, 1910] 



SCIENCE 



955 



air conditions made on Alay 18, 19 and 20, 

 Blue Hill Observatory and the United States 

 Weather Bureau furnished the American 

 contribution. The former institution sent 

 up pilot balloons at the observatory and 

 sounding balloons at Pittsfield, Mass., while 

 the Weather Bureau made their usual kite 

 flights at Mount Weather and sent up sound- 

 ing balloons at Omaha, ISTebr. After ascend- 

 ing to a height of about eleven kilometers 

 and passing through air at a temperature of 

 about — 50° Centigrade, one of the four bal- 

 loons sent up from Pittsfield descended in the 

 Atlantic Ocean just, east of Block Island, 

 where it was recovered by the crew of a fish- 

 ing schooner. Ajojeew H. Palmer 

 Bltje Hill Obsebvatoby, 

 Hyde Pabk, IIass., 

 May 26, 1910 



SPECIAL ARTICLES 

 A SIMPLE AND ECONOMICAL AQUAEIUM AERATOR 



A SUCCESSFUL aquarium is a very rare ob- 

 ject in undergraduate biological laboratories. 

 The difficulties to be overcome in running an 

 aquarium are generally thought to be so great 

 that few are ever started; and if an animal 

 happens to survive, it is usually considered an 

 exceptional or an accidental case. There are, 

 of course, good reasons for such a small num- 

 ber of aquaria. In the long run the various 

 causes of non-success may generally be traced 

 to two fundamental causes. These are insuffi- 

 ciency of food, and an insufficient supply of 

 oxygen. In many cases the first of these de- 

 fects is remedied by removing the second — an 

 insufficient supply of oxygen. For when the 

 food of an animal consists of living organ- 

 isms, it is tolerably certain that there must be 

 about the same amount of oxygen in the water 

 for the food organisms to develop as is needed 

 by the animal that feeds upon them. In other 

 words, whenever the conditions are such that 

 the food organisms can grow, the animal feed- 

 ing upon them is also pretty certain to be 

 able to live. Our chief concern seems to be 

 therefore to establish a proper supply of oxy- 

 gen to the water, and then knowing the food 

 habits of the animal which we wish to put in 



the aquarium, we should not experience any 

 great difficulty in keeping the animal alive. 



There are many ways of aerating an aqua- 

 rium, as might be expected, but there are al- 

 ways certain drawbacks, either in the simplic- 

 ity of the apparatus, or in the economy of 

 running it, or again in the irregularity of its 

 action. The apparatus described below is the 

 best which has yet come to my notice, as far 

 as simplicity, economy and regularity of de- 

 livery of air are concerned. The apparatus is 

 in use in the writer's laboratory and is giving 

 perfect satisfaction on the three scores men- 

 tioned above, in addition to the important one 

 of keeping the animals alive. 



Before describing the apparatus it may be 

 well to say that the aquarium should be 

 stocked with water from the pond or stream 

 from which the animal was taken, and not 

 with " city water." The latter is often treated 

 with chemicals to render it more fit for do- 

 mestic use, as the precipitation of suspended 

 clay by means of alum, etc. Water which has 

 undergone this treatment is sometimes del- 

 eterious to animals, especially the lower forms. 



Description of the Apparatus. — The tube A 

 is of rubber and connects the aerator with the 

 hydrant. Tube B is the " miser." It conveys 

 the water from A to the bottle E. As the 

 water passes a and h, which are small open 

 side branches in B, a quantity of air is sucked 

 in and carried with the water into the bottle 

 E. To obtain the maximum efficiency of the 

 water as carrier of air, the tube B is drawn 

 out to fine bore and bent at c and d in the 

 form shown. The small bore causes all the 

 water which passes down B to form drops fill- 

 ing the whole bore of B. Otherwise much of 

 the water would run down the sides of the 

 tube without pushing a quantity of air ahead 

 of it. The tube C is of glass, or glass and 

 rubber, as convenient, and carries the water 

 brought down B into the aquarium through 

 the opening k. The bulb g is for the purpose 

 of preventing drops of water (which occasion- 

 ally splash against /) from passing into the 

 aquarium. The tube D is of glass and is what 

 is known as a constant level siphon. Its pur- 

 pose is to carry out the water which is col- 



