October 21, 1922] 



NA TURE 



557 



The Distribution of Temperature in Scandi- 

 navia. — The Meteorological Institute of Sweden has 

 published an important paper and series of charts 

 bv Mr. H. E. Hamberg on thermosynchrones and 

 thermoisochrones in the Scandinavian peninsula 

 (Bihang till Meteorologiska lak ttagelser, Bd. 60, 

 191 8 (1922)). In tables and charts, founded on 

 the observations of 232 Swedish and 83 Norwegian 

 stations, Mr. Hamberg gives the mean annual dates 

 at which certain temperatures reign. The tempera- 

 tures are reduced to sea-level for this purpose, 

 although Mr. Hamberg fully realises that for certain 

 geographical uses the value of the charts is thereby 

 lessened, and he gives two pairs of charts, spring and 

 autumn, one for 12° C. and the other for 0° C, 

 in which the actual temperatures are utilised. A 

 second series of charts indicates the average number 

 of days with a temperature above or below certain 

 figures. The curves on these charts Mr. Hamberg terms 

 thermoisochrones. The charts, which are small but 

 verv clear, are most useful for geographical purposes. 



Spell of Warm Winters in Europe. — The 

 abnormal winter warmth recently experienced in 

 Central Europe, embracing England, is dealt with in 

 the Meteorological Magazine for September by Mr. 

 C. E. P. Brooks, of the Meteorological Office. A 

 chart is given showing the differences of the mean 

 temperatures for the winter, comprised by the 

 months December, January, and February, for the 

 years 191 1 to 1920, and the long period averages for 

 the combined winter months, mostlv covering the 

 years 1851 to 1910. At Budapest the winters of 

 the past ten years have on the average been more 

 than 4 : F. warmer than the normal winter. At 

 Zurich the excess is 2°-6 F. ; at Paris, 2°-i F. ; and 

 at Kew, i°-8 F. On the Atlantic sea-board the 

 winters of the decade in question have been slightly 

 colder than the normal. There is no appreciable 

 difference of temperature for the rest of the year, 

 the summer months for the years 191 1 to 1920 having 

 been, on the whole, somewhat cooler than the average. 

 The abnormal warmth of the winters was not confined 

 to low levels ; the mean winter temperature for the 

 ten-year period at St. Gothard, 6877 feet above 

 sea-level, is i°-9 F. above the normal. The author 

 suggests a tentative explanation connecting the ab- 

 normal warmth with the general decrease of sunspot 

 numbers since the nineteenth century. Taking the 

 mean winter temperature at Greenwich for the 

 ten-year period, 191 1 to 1920, it is i°-5 F. above the 

 60 years' average, and the mean was above the normal 

 in 8 winters out of 10, the excess being more than 

 3 F. in 4 winters. In the ten-year period from 

 1886 to 1895 the mean winter temperature at 

 Greenwich was i°-9 F. below the normal for sixty 

 years, and in 8 winters out of 10 the mean was below 

 the average, the deficiency amounting to 3 F. or more 

 in 3 winters ; this is a different period from that 

 given by the author and with an opposite effect. 



Glare from Motor Headlights. — The descrip- 

 tions of motor headlights exhibited at the meeting 

 of the Optical Society on May 1 1 will be found in 

 part 4 of volume 23 of the Transactions of the Society, 

 together with a report of the discussion of the 

 conditions which a satisfactory headlight should fulfil. 

 In America these conditions are that 100 feet ahead 

 of the car at a point 5 feet above the horizontal, the 

 illumination must not exceed that due to a lamp of 

 750 candle power. The conditions laid down in 

 this country by the Ministry of Transport relate to 

 the width and height of the beam and place no 

 restriction on its intensity. The reconciliation of the 

 requirements of the driver and the pedestrian or 

 driver he is approaching is difficult, but the general 

 opinion of those who took part in the discussion 



NO. 2764, VOL. I IO] 



appeared to be that the beam should have a candle 

 power of 3000 in a direction half a degree below 

 the horizontal and be reduced to 500 or 600 candle 

 power in a direction one degree above the horizontal. 

 As the glare effect is due to contrast, it was further 

 suggested that the car body and the road at the side 

 of the car should be illuminated to some extent as 

 well as the road in front. 



A New Theory of Vision. — A photo-electric 

 theory of vision has recently been put forward by 

 Dr. F. Schanz of Dresden and has been discussed in 

 the Zeitschrift fur Augenheilkunde. At present it is 

 incomplete, but according to a paper in vol. 54 of 

 the Zeitschrift fur Sinnesphysiologie the author hopes 

 to fill in the gaps by work on which he is at present 

 engaged. In outline it is as follows : Light on enter- 

 ing the eye is absorbed by the visual purple, which 

 as a result emits electrons at speeds which depend 

 on the wave-length but not on the intensity of the 

 incident light ; that is, the visual purple is photo- 

 electric. The electrons impinge on the rods and 

 cones and produce the sensation of light. If their 

 velocities do not differ widely they are equalised 

 during their passage to the rods and cones and 

 produce a single sensation corresponding to the 

 mean velocity ; but if they differ materially the 

 interval between their emission and their arrival 

 at the rods and cones is not sufficient to equalise 

 them and they produce distinct sensations. Over 

 a range of wave-lengths of 1 x io -4 cm. equalisation 

 is produced, but if all wave-lengths over a range 

 double this are present, the sensation of white is pro- 

 duced, whether the range be e.g. from 4 to 6 or from 

 6 to 8 x io _1 cm. 



Testing for Vitamins. — Investigators are search- 

 ing actively for some chemical means of recognising 

 the presence of the vitamins in food materials, and 

 the discovery of such a test would enormously increase 

 the facility of research on these elusive substances. 

 So far all the suggestions made have failed to with- 

 stand a critical examination. In a recent paper in 

 the Analyst, Messrs. Drummond and Watson point 

 out the close relation which exists between the 

 presence of vitamin A in fats and the well-known 

 reaction given by liver oils, which consists in the 

 production of a purple coloration when the oil is 

 dissolved in an organic solvent and a drop of sulphuric 

 acid is added. All the liver oils of mammals, birds, 

 and fish examined by the authors gave the reaction, 

 but they also find that it is given, although less 

 strongly, by the body fat of some animals and by 

 butter. In striking agreement with the behaviour 

 of vitamin A, the power of producing the coloration 

 is lost when a current of air is passed through the 

 fat at 100 C. but not when the fat is heated at this 

 temperature in absence of air. Again, when the fat 

 is hydrolvsed it remains, with the vitamin A, in the 

 unsaponifiable fraction. Moreover, the intensity of 

 the reaction was found to be roughly proportional 

 to the vitamin A content of a series of fish-liver oils. 

 The livers and fat of pigs and rats fed on diets deficient 

 in vitamin A did not give the reaction, but this 

 reappeared when the <1< li made good. It 



is obvious that there is a close parallel between the 

 two properties, and the authors, without claiming 

 that the test actually indicates the presence of the 

 vitamin, suggest " that the association may be of 

 some significance." The necessity for this caution 

 is indicated by the facts that although the marine 

 diatom Nietzschia has been shown to be rich in 

 vitamin A the oil extracted from this organism did 

 not give the purple colour test with sulphuric acid. 

 A similar negative result was obtained with plankton oil, 

 although the reaction was given by certain marine algae. 



