188 



SCIENCE 



[N. S. Vol. LI. No. 1312 



eight of the olive-green water form and seven 

 of the Vermillion land form were examined. 

 Every one of the former was abundantly sup- 

 plied with the parasites, but only two of the 

 land forms were infected. 



All that is necessary to obtain living speci- 

 mens of the trypanosomes for study is to 

 snip off a little piece from the end of the tail, 

 and then squeeze out several drops of blood 

 on each slide. A cover glass can be added 

 directly or a ring of vaseline m.ay first be 

 spread around the blood so that the preparation 

 will be sealed when the cover glass is put in 

 place. In such a preparation the spiral move- 

 ment of the organism is evident, and the 

 flagellum and undulating membrane are easily 

 observed in action. The nucleus and other 

 structures are clearly revealed in dried films 

 stained with Wright's or Leishman's stains. 

 Obtain a drop of blood near one end of a 

 clean slide. Place the end of another slide 

 near the drop of blood at an angle of about 

 30 degrees with the shorter end of the slide. 

 Draw this slide along until it touches the 

 drop. When the blood has spread along the 

 edge, push the slide fairly rapidly toward the 

 other end. A thin even film will result 

 covering about one half of the slide. Allow 

 this to dry. Then place a few drops of the 

 stain on the film and allow to remain one 

 minute. Add double the volume of distilled 

 water and after five minutes wash the film 

 with distilled water, and dry in the air. 

 Balsam and a cover glass may then be added 

 but the stain will fade. If oil immersion ob- 

 jectives are available no cover glass should be 

 used but the oil placed directly on the iUm, 

 and after the examination is completed this 

 oil may be wiped off with lens paper or washed 

 off with xylol. The stain may be obtained in 

 small 0.1 gram tubes. This amount is dis- 

 solved in 10 c.c. of pure methyl alcohol and 

 is then ready for use. R. W. Hegner 



School op Hygiene and Public Health, 

 The Johns Hopkins Universitt 



horizontal rainbows 

 To THE Editor op Science : With respect to 

 Eeese's accoimt of an " unusual form of rain- 



bow" in Science for December 12, 1919 (Vol. 

 L., p. 542), it may be said that, in Europe, 

 rainbows on the surfaces of ponds and lakes 

 have been reported from time to time diu-ing 

 the past fifty years. They have been observed, 

 also, on several bodies of water in Japan 

 during the past few years and the investiga- 

 tors of that country have given some atten- 

 tion to the mathematical explanation of these 

 phenomena. 



In the United States these spectral displays 

 have been seen frequently on the surface of 

 Lake Mendota at Madison, Wisconsin, during 

 the past ten or twelve years. Some of these 

 displays have been unusually brilliant and 

 varied; double and triple primary bows to- 

 gether with a secondary bow have been noted 

 at times. These phenomena have been de- 

 scribed in the Monthly Weather Review for 

 February, 1916 (Vol. 44, p. 65). 



The complete bows that have appeared on 

 the surface of Lake Mendota possessed a very 

 different outline from the diagram shown by 

 Reese. They were parabolic in shape instead 

 of circular; neither did they possess an in- 

 verted segment connecting the outer extrem- 

 ities as in his figure. 



As far as the present writer is aware, these 

 horizontal rainbows have been reported for 

 only two lakes in this coimtry, namely. Lake 

 Mendota and the lake referred to by Reese. 

 This seems to indicate that it is not a wide- 

 spread phenomenon, or else other observers 

 have not taken the trouble to publish accounts 

 of their observations. It would be interest- 

 ing to know whether these spectral colors 

 have been seen on any other bodies of water 

 in this country. 



Chancey Juday 



Madison, Wisconsin 



chemistry applied to commerce 

 The divorce of science and industry, which 

 has long been a noisesome skeleton in our 

 economic household, is fast being annulled. 

 " During the war, American industry acquired 

 - — or had thrust upon it — a wholesome respect 

 for American science," Drug and Chemical 



