May 5, 1921] 



N4mR^i, 



3C9 



ties, making altogether an , attractive record of a, 

 year's endeavour in the field of natural history. A 

 new feature upon which the society is to be con- 

 gratulated is the opening of a laboratory in which 

 members can carry out a certain amount of indepen- 

 dent work. 



Mrs. Mabel C. Wright describes a new concho- 



stracan genus under the name Limnestheria from the 

 Coal Measures of Kilkenny, which have been fertile 

 in interesting fossil forms, ranging from limuloids 

 to amphibia (Proc. Roy. Irish Acad., vol. xxxv., 

 sect. B, p. 187, 1920). The specimens, including 

 antennae and limbs, are beautifully preserved in 

 pyrite in Carboniferous shale, and were received by 

 the Geological Survey of Ireland from a depth of 

 830 ft. in the cores of a recent boring. The author 

 concisely reviews the eight known living genera of 

 Conchostraca, and shows how Limnestheria, on the 

 analogy of the highly fertile Limnadia, illustrates 

 the geographic and climatic conditions of the epoch in 

 the Leinster coalfield. 



Entomological Bulletin No. 872 of the U.S. Depart- 

 ment of Agriculture deals with " Insect Control in 

 Flour Mills." Mr. E. A. Back, the author of the 

 publication, confines his attention to the Mediter- 

 ranean flour-moth, which is by far the most serious 

 pest. He divides control measures into three classes : 

 Preventive, including attention to cleanliness ; natural 

 control by means of parasites; and artificial control. 

 A large proportion of insect infestation in flour-mills 

 is directly due to lack of cleanliness, and much may 

 be achieved by thorough cleaning once every five 

 weeks throughout the summer months. The utilisa- 

 tion of parasites cannot be depended upon in any part 

 of the United States. Artificial control has been 

 advocated along various lines, and there have finally 

 emerged two measures that have now proved their 

 value, viz. fumigation by hydrocyanic acid gas and 

 control by heat. The former method is disagreeable 

 and dangerous, and elaborate precautions have to 

 be taken. There are also certain beetle pests which 

 are more resistant to the effects of the gas, and the 

 most satisfactory method for controlling all classes of 

 mill-infesting insects is the application of a tempera- 

 ture of 118° to 125° F. To carry out this process 

 effectually the installation of radiators or radiation 

 surfaces is necessary. It has been estimated that 

 this can be fitted up sufficiently economically in an 

 average-sized mill to pay in five years for the cost of 

 its introduction ; the heat does not affect the baking 

 qualities of the flour. 



The United States Geological Survey has published 

 a preliminary summary of the mineral resources of 

 the United States in 1919. The value of such statistics 

 of production, etc., at an early date is very obvious^ 

 although it is to be hoped that in future years their 

 compilation may be completed in less than nine months. 

 The importance of the present set of statistics lies in 

 the fact that they include 1913, the last pre-war year; 

 1918, the year of the maximum intensity of produc- 

 tion for war purposes; and 1919, the first year of the 

 return towards more normal industrial conditions. 

 NO. 2688, VOL. 107] 



Thus, to take the most important of all, namely, coal, 

 it is shown that the production in 1913 was 569,960,219 

 (short) tons; in 19 18, 678,211,904 tons; and in 19 19, 

 about 544,263,000 tons. The position is similar in 

 most other important minerals, the output in 1919 

 being considerably less than the intensive figures 

 reached in 19 18, but in most cases not far behind 

 those of 19 13. The importance of having such 

 statistics as these available at an early date, even 

 though they may not be absolutely accurate and may 

 need some little later revision, cannot be too stronglv 

 emphasised. 



The weather was so persistently mild and dry 

 during the past winter that a comparison with 

 previous winters may be of interest. The Greenwich 

 mean temperature for each of the six months 

 October, 1920-March, 192 1 was abo\'e the average. 

 The mean for the whole period was 450° F., the 

 excess for the six months amounting to 26°. The 

 greatest excess was 7° for January, while for March 

 the excess was 4°. There have been two milder 

 winters since 1841, that of 1898-99 having a mean 

 of 45-4°. while for 19 13-14 the mean was 45-2°. 

 For each of the winters 1911-12 and 1876-77 the 

 mean was 450° F., in absolute agreement with the 

 past winter. Frost occurred in the shade on thirty 

 nights during the past six winter months, the greatest 

 number of frosty nights, ten in number, having 

 occurred in November. There have been eight winters 

 since 1841 with fewer frosts, the least number being 

 nineteen recorded in 1883-84. Rainfall was below 

 the average in each month except perhaps December, 

 which, however, was dry compared with the Greenwich 

 average for a hundred years. The total fall for the 

 winter was 687 in., which is about 5 in. less than the 

 normal. There have been only three drier winters 

 since 1841 ; the driest was 1879-80 with 554 in. of 

 rainfall, followed by 1858-59 with 665 in. and by 

 1897-98 with 685 in. 



The equation UV=-f, where U and V denote 

 respectively the distance of object and image from the 

 focal planes of a thin lens, is not so well known as 

 the equation i/v-i/u=i/f, which gives the distances 

 from the lens itselL We have received a booklet from 

 Prof. Mohd. A. R. Khan, Nizam College, Hyderabad, 

 in which the former equation is graphed and applied 

 in detail to different elementary cases with the view 

 of encouraging its use by students of elementary 

 optics. 



We have received from Messrs. R. and J. Beck, 

 68 Cornhill, E.C.3, a catalogue of microscopes and 

 microscopical apparatus. The standard London 

 microscope. Model I., has been designed to fulfil the 

 specification prepared by the British Science Guild 

 for a standard microscope, and is supplied in four 

 types. Stand No. 321 1, which is suitable for ordinary 

 bacteriological work, includes condenser, three eye- 

 pieces, I in., ^ in., and yV in. o.i. objectives, dark- 

 ground illuminator and stop for the oil-immersion 

 objective, and a set of Sloan objective changers, and 

 is listed at 33Z. iii-. (December, 1920). A detachable 

 form of mechanical stage costs an additional 61 A 



