M4 



NATURE 



[March 3c 



). 1 ' ; 1 1 



resistance to the formation of new film, the fiim-tenaion 

 in th(.' front will be greater than in the rear, and the film 

 will be (Ir.ifjfjed from the rear to the front of the bubble, 

 and in its movement will carry the water in contact with 

 it, thus causing the forward current a. \% the supply of 

 liim has to travel in a narrow stream in the middle of 

 the space between the two glasses, it will flow with con- 

 siderable velocity, as it has to provide film for all the area 

 dragged on by contact with the glass surfaces. 



John Aitken. 

 Ard'-nlcn, Falkirk, N.B. 



Insect Inielligence. 



Mv friend Prof. Hughes's story about a fox's cleverness 

 in getting rid of his fleas induces me to recount an 

 instance of insect intelligence which I witnessed about fifty 

 years .igo at lillmstead in Essex, a place teeming with 

 insect life. There was a narrow border round the wall 

 of my house ; on this I noticed one day a large fly of the 

 ichneumon family straddling over and dragging a green 

 caterpillar bigger than itself. I watched it crawling for 

 some thirty or more yards round an angle of the house 

 until it came to a corner protected by a projection of the 

 wall. Here it deposited the caterpillar, and removed one 

 by one a little heap of small stones. This disclosed a 

 cylindrical hole in the ground, into which the fly descended 

 tail first, dragging the caterpillar after it. It then came 

 out, and again went down, apparently stamping the cater- 

 pillar close, and may probably at the same time have laid 

 ^" ^fig- It then came up, replaced the stones so as to 

 hide the orifice, and flew away. 



This probably was only an instance of the mode of pro- 

 ceeding of the whole species, but notice what it involves. 

 The insect must have dug the deep hole and hidden the 

 entrance to it carefully for future use, and it must have 

 remembered its position so as to find it again from what- 

 ever quarter where it may have chanced to find its prey. 



Graveley, Huntingdon. Osmond Fisher. 



Reflection of Ultra-violet Rays by Snow. 



Allow me to make the following short statement in 

 the columns of Nature, 



During the past winter we have had frequent snowfalls 

 here in Switzerland, these being followed very often by 

 bright sunshine. I availed myself of these occasions to 

 determine to what extent the spectra of sunlight, reflected 

 by snowfields, reaches into the ultra-violet. To this end 

 I took numerous photographs of the spectrum produced 

 by this reflected light, the angle being 45°. The time of 

 exposure varied from i second to 20 seconds, with a slit 

 opening of 005 mm. The resuUs showed that this spec- 

 trum of reflected sunlight reaches up to 295 yni. The 

 tests were made between 10 and 12 o'clock a.m. at an 

 altitude of 630 metres above the sea-level. 



Comparing the results with those of Cornu, we must 

 conclude that the ultra-violet rays are reflected by snow- 

 fields almost in their entirety, and hence the powerful 

 action of this light cannot be called into question. It 

 would therefore be advisable at all times, during a period 

 of snow and sunshine, to protect the eyes from the 

 injurious effects of these ultra-violet rays by using glasses 

 which will not permit these rays to pass. 



J. V. KOWALSKI. 



University de Fribourg, Institut de Physique, 

 March 20. 



Assil Cotton. 



A FORM of cotton has been produced, by selection in the 

 field from superior growths of Mit Afifi, which is said 

 to be a pure strain and similar to the Mit Afifi of twenty 

 years ago. This form is known by the name of "Assil," 

 meaning "of pure original strain." 



In order to prevent any misconception occurring that 

 by substituting " Assil " for the present impure Mit .Afifi 

 the introduction of a new variety is advocated, it is recom- 

 mended that this form of cotton be for the present referred 

 to as "Assil Afifi." G. C. Dudgeon. 



(liirecior-General.') 



Department of Agriculture, Cairo, March 21. 



NO. 2 161, VOL. 86] 



INSURANCE AGAINST RAL\. 



A.SC'HE.ME of holiday insurance against rain has 

 been put forward by the Excess Insurance Com- 

 pany, and has been described in considerable detail in 

 The Times of March 21 and 22. It applies to the 

 period from May 1 to September 30, at a series of 

 .sixty-three sea-coast towns on the south and east of 

 England. It is stated that the daily readings of raiu 

 gauges at the towns in question (or in some cases 

 where there is no local observer at a neighbouring 

 town), will be supplied to the company by the town 

 clerks, or "culled from the lists of the .Meteoroh)gical 

 Office." Four forms of policy are proposed, desig- 

 nated respectively Pluvius A, 13, C, and D. Policy A 

 provides lor payment for each separate week in which 

 there is rain on more than two days, amounting on 

 each to more than o'2o in., and the premium is to be 

 one-eighth of the compensation to be paid per week. 

 Policy B provides for payment for every day on which 

 the rainfall exceeds 020 in., and the weekly premium 

 is equal to one and a half times the compensation 

 offered per day. Policy C provides for payment for 

 the second and each additional rain-day in a week 

 on which the rainfall exceeds 01 5 in., and the weekly 

 premium is equal to the daily compensation, and 

 Policy D provides for four days, payment being made 

 for every day on which more than 020 in. falls, and 

 the premium for the four days is equal to the com- 

 pensation per day. 



The interest of the proposition lies in the fact that 

 the rain for which compensation is to be paid may 

 fall entirely at night and not affect the enjoyment of 

 the holiday at all, and as much compensation will be 

 paid, so far as we can judge, for a thunder-shower of 

 ten minutes' duration yielding just more than 020 in. as 

 for a day of uninterrupted rain for twenty-four hours, 

 yielding two or three inches. As there is no necessity 

 laid on the assured to prove damage or even to go 

 near the place where the rain is to be measured, it is 

 apparent that a question may arise as to whether the 

 transaction in certain cases is legitimate insur- 

 ance or mere gambling. The assured and the 

 company are bound by the terms of the policy to 

 accept the readings of daily rainfall supplied from a 

 specified rain gauge as binding, but no information 

 is given in the articles from which we quote as to the 

 limits of the rainfall day, e.g. whether it is to count 

 from 9 a.m. to 9 a.m., as in ordinary records, or from 

 7 a.m. to 7 a.m.; as at the daily reporting stations of 

 the Meteorological Office. No indication is given as 

 to how the records from those stations which read 

 rainfall to three places of decimals are to be inter- 

 preted ; for instance, one observer records 0204, where 

 another for the same quantity in the measuring glass 

 records o'20 ; the first records 0206 where the other 

 records 02 1 ; and when the first records 0205 the 

 second mav read o"2o or 02 1 with equal truth; but 

 the alternative he chooses would decide the payment 

 or non-payment of perhaos a considerable sum as 

 compensation. 



It must also be remembered, as Dr. H. R. Mill 

 points out in The Times of March 23, that in summer 

 the rainfall varies very greatly in a short distance, 

 and unless the assured stays very near the rain gauge 

 he may experience totally different weather from that 

 which it records. Here, however, the chance is even 

 of the rainfall being more or less than is recorded — 

 in the one case he may be damaged without com- 

 pensation, in the other he may be compensated with- 

 out damage. Dr. Mill considers that there are no 

 data yet elaborated on which a fair basis for an 

 equitable and practicable scheme of insurances against 

 rain risks can be framed. 



