June 3, 1910] 



SCIENCE 



857 



tlie honeycombed ice remains intact and be- 

 comes nothing more than a collection of ver- 

 tical ice needles ready to topple over at the 

 slightest touch. Outwardly this sheet of 

 instability appears firm and compact. Dur- 

 ing the period of rotting the temperature of 

 maximum density is slowly advancing up- 

 wards towards the ice sheet. Below the sur- 

 face of maximum density convection of heat 

 brings more and more warm water up from 

 the bottom. There must be then a definite 

 surface in the water at 4° C, below which 

 the temperature is kept fairly uniform by 

 convection and above which there is no move- 

 ment in the water to disturb the existing 

 temperature gradient up to the ice sheet. As 

 soon as the 4° surface reaches the under side 

 of the already honeycombed ice the change of 

 temperature and movement of water must be 

 fairly sudden, causing a rapid collapse of the 

 whole structure. This no doubt accounts for 

 the characteristic rattling noise when the 

 phenomenon takes place. The ice needles 

 soon melt in the warm water, which gives rise 

 to the general belief that the ice sinks. 



H. T. Barnes 



McGiix Univeesity, 

 April 16, 1910 



PLANKTON 



The article of Professor Chas. E. Wood- 

 ruff in Science of April 22 recalled to me ob- 

 servations I had made of phosphorescence of 

 the sea. In connection with astronomic work 

 I have sailed many seas, and have circumnavi- 

 gated the globe in completing its astronomical 

 girdle in longitude. 



In the waters along southeastern Alaska, 

 an area of fog, rain and little sunshine, I had 

 observed most exquisite phosphorescence of 

 the sea. When being rowed from the govern- 

 ment steamer ashore, every dip of the oars 

 showed them surrounded by that delicate 

 bluish light of phosphorescence. When I 

 walked over the beach of the receded tide 

 every footprint was a blaze of this same light. 



Some years subsequently when I started on 

 my work round the world I looked forward 

 with pleasure to beholding the grand phos- 



phorescence of the tropics, under the belief 

 that in the warmer waters and bright 

 sunshine, the plankton — the cause of the 

 phosphorescence — would be more densely dis- 

 tributed. In this however I was sadly disap- 

 pointed. 



In none of the tropical seas did I see any 

 phosphorescence that could at all compare 

 with what I described above. In vain have I 

 stood at night at the bow or side of the 

 steamer on a smooth sea watching for a fine- 

 display of phosphorescence. Now and then 

 the comb of the small wave as the vessel 

 parted the waters showed a fringe of the- 

 bluish light, and nothing more. 



Arrhenius in his " Lehrbuch der Kos-- 

 mischen Physik," p. 376, says that the phos- 

 phorescence of the sea " is most beautifully- 

 developed in the tropics," which is not my ex- 

 perience. Major Woodruff's explanation 

 and application to the tropics of the destruc- 

 tive and lethal effect of light on the plankton 

 agrees very well with my observations on the- 

 phosphorescence of the sea in different parts, 

 of the world. 



Otto Klotz, 



Obsebvatoet, Ottawa, 

 April 28, 1910 



\tHANASIUS KIROHER and the GERi£ THEORY OF 

 DISEASE 



In reference to Dr. Riley's note in Science 

 for April 29, I am glad to make a prompt 

 amende honorable for a hasty error of com- 

 mission in regard to the magnifying power of 

 Leeuwenhoek's microscopes, but it is difficult 

 to see how any injustice has been done to 

 Athanasius Kircher thereby, since the quality 

 of his magnifying glass seems principally a 

 matter of conjecture. If we accept Osier's ad- 

 justment of the matter of priority in the bac- 

 terial theory of infectious diseases, then the 

 medical fame of the remarkable priest who 

 was also a mathematician, physicist, optician, 

 pathologist, Orientalist, musician and virtu- 

 oso, rests rather upon his seven experiments 

 upon the nature of putrefaction' than upon his 



' " Kircher Scrutinium," Komae, 1658, caput 

 VII., pp. 42-49. , 



