66 



SCIENCE-GOSSIP. 



of great delicacy, and are used in the following 

 way : 



A sufficient quantity of water is taken to fill all 

 of the tubes shown in the figure, and the dish up 

 to the mark D E. This is tinted with a sufficient 

 quantity of a freshly-made solution of haematoxylin. 

 The colour should be a very pale hue of red. The 

 tube A is then filled, and the rubber stopper, with 

 its penetrating quill-tube, is inserted, the last 

 bubble of air is forced out by pressure, and the 

 tube suspended as shown. The remainder of the 

 solution is acidified with carbon-dioxide from the 

 lungs, blown into it through a glass tube. The 

 brownish-yellow tint having developed, tubes B 

 and C are filled with the solution, and into C some 

 clean, living diatoms are put. Both are then 

 corked and hung as figured, the quill-tubes dipping 

 below the surface of the liquid in the dish. 

 These quill-tubes, which allow the pressure 

 within the larger tubes, due to gas or to 

 expansion from heat, to relieve itself into the 

 dish, are drawn down to a very small opening in 

 order to lessen diffusion of liquid up or down and 

 to confine the diatoms. The apparatus is now 

 exposed to bright light— if to direct sunlight so 

 much the better, since the action is then more 

 rapid. Gas arises from the diatoms in tube C, 

 and simultaneously the colour of the liquid, which 

 is at first like that in B, begins to change. 

 Within fifteen minutes, under proper conditions, 

 the colour has again become almost or quite as red 

 as that in tube A. The carbon-dioxide has now in 



large measure disappeared from the solution. The 

 action continues, and the colour in tube C deepens 

 rapidly, showing oxidation ; and this action 

 continues until the colour is quite blood-red or 

 even, in case much lime is in the water, until 

 bluish lakes are formed in clouds. The ceasing 

 of the action may, conceivably, be determined by 

 exhaustion of every trace of carbon-dioxide, but 

 data on this head are wanting as yet. At all 

 events the evolution of gas goes on long after 

 the colour reaction of carbon-dioxide has dis- 

 appeared. 



The experiment may be varied in the following 

 manner : All of the tubes are filled with the 

 normal, non-acid, reddish solution of haematoxylin. 

 Into A is put a living snail, into B live diatoms, 

 and C is allowed to remain for comparison. The 

 whole apparatus being exposed to sunshine, A 

 pales rapidly under the influence of the carbon 

 dioxide from the snail, while B as rapidly darkens 

 and reddens compared with C, owing to the oxygen 

 from the diatoms. This result, so significant, is 

 obtainable in a very few minutes. 



The diatoms selected for the above experiments 

 were the long, broad filamentous forms of Eunotia 

 (E. major of Rabenhorst), which are peculiarly 

 applicable, because it is easy to procure them in 

 sufficient abundance, and to free them, under a 

 dissecting microscope, from any accompanying 

 algae that might, by their presence, tend to 

 cast doubt upon the conclusiveness of the 

 results. 



THE COMING OF THE RAINS. 

 By Stanley S. Flower, F.Z.S. 



(Communicated by Sir William 



A LL those who have been through an Indian 

 ^* "hot weather" know the extraordinary 

 difference " the coming of the rains " makes in 

 the amount of visible animal life, which to those 

 who have not experienced the change seems almost 

 incredible. In Siam it isjust the same — for months 

 there is no rain. During January and February 

 the climate is delightful — warm, dry days, with cool 

 refreshing nights ; in March and April comes the 

 hot weather, the thermometer sometimes up to 102 

 degrees in the shade by day and only down to 95 

 degrees at midnight. The broad, alluvial plains 

 between the rivers are a parched desert, the paddy 

 fields being hard and sun-cracked, with no vestige 

 of green. Birds are plentiful enough. All day 

 long one hears the monotonous " pook, pook, pook " 

 of the hot-weather bird (Xantholaema haematocephala) 

 and the almost equally distracting cry of the koil 

 (Eudynamis honorala), and one wonders what 



H. Flower, K.C.B., F.R.S.) 



Rudyard Kipling was thinking of when he wrote 

 of " koil, little koil," and describes it as " the 

 Indian nightingale," but one agrees when he 

 sings : 



"In my ears the knell of exile your ceaseless, bell-like 



speech is — 

 Can you tell me aught of England, or of Spring in England 



now ? " 



The animal world seems dead were it not for the 

 birds and the flying foxes (Pteropus medius) which 

 every evening leave their roosting-tree by the 

 village temple, where the Buddhist priests hold 

 them sacred. These large bats fly off to such trees 

 as they know to be in fruit. There are also a few 

 monkeys and squirrels. True, many geckoes are 

 to be seen about the houses at night, fleas swarm 

 to an obnoxious extent in the dry dust of some of 

 the paths, and " sand flies " abound, those irritating 

 little insects just large enough to see but not to 

 catch, which have a special penchant for biting 



