May 4, 1916] 



NATURE 



207 



greatest value to all interested in any aspect of this 

 very important industry. In this connection attention 

 may be directed to the very full account of the natural 

 gas industry to be found in a paper by Dr. J. A. L. 

 Henderson, read on March 21 before the Institution of 

 Petroleum Technologists. 



In the Rassegna Nazionale, xxxviii., (2), i, a fort- 

 nightly review dealing mainly with politics and 

 literature, science is represented by a popular article 

 on "Infinity" by Pietro Pagnini, in which the pecu- 

 liarities of infinite space, time, and number are dis- 

 cussed. 



About the first fortnight of March, 1915, the peach 

 blossoms in the gardens at Rome were damaged by 

 the larvae of a micro-moth identified as Recurvaria 

 nanella. An account of the biology of this insect is 

 given by Armando Mignone in the Atti dei Lincei. 

 XXV., (i), 3, 5. It belongs to the family Gelechiidae, 

 and the description of the European form appears to 

 be identical with Scott and Paine 's observations in 

 the United States. The imago spends most of the 

 day resting with wings closed on the peach and cer- 

 tain other fruit trees. The larvae, which are hatched 

 in the autumn, are leaf-miners, making long tunnels 

 in the leaves. In the winter they come out and 

 hibernate in places where they are almost invisible, 

 investing themselves with a silk covering, and the fol- 

 lowing spring they emerge and attack the young buds. 



SPECiiiL Publication No. 33 of the Department of 

 Commerce of the United States Coast and Geodetic 

 Survey deals with the results up to the present time 

 of the magnetic survey of the country and of the 

 adjoining seas. These results are given in the form 

 of tables, and are embodied in a chart to a scale of 

 about no miles to the inch. The isogonic lities, or 

 lines of equal deviation of the compass from true 

 north, are drawn for each degree of deviation from 

 24° east in the north-western States to 24° west in 

 the north-eastern States. The date for which they 

 hold is January i, 1915. In the north-western States 

 the isogonic lines run nearly east and west, in the 

 central States nearly north and south, and in the 

 eastern States north-west to south-east. In the west 

 afid south they are fairly regular in shape, but in the 

 east and in the regions south of the great lakes they 

 are much folded. Along a line from Florida to a 

 point 100 miles west of Lake Superior there is no 

 secular change in the deviation of the compass; at 

 points east of this the north end of the compass needle 

 is moving to the west at a rate which exceeds six 

 minutes of arc per annum in the north-eastern States, 

 and at points west of the line the north end is moving 

 to the east at a rate which is nearly four minutes 

 per annum in the south-western States. 



The Royal Engineers' Journal for April contains an 

 article on explosives compiled from one which ap- 

 peared originally in the Revue Militaire Suisse. All 

 the more generally used explosives are described, with 

 some account of their manufacture. No mention is 

 made, however, of modern methods of making nitro- 

 cellulose ; only the old pot method is described. Simi- 

 larly, recent improvements in the manufacture of 

 nitroglycerine are not referred to. Reference is made 

 to the interesting explosive residue left when a 

 rhodium-zinc alloy is dissolved in hydrochloric acid, 

 this residue exploding when heated to 400° C. in a 

 vacuum. In conclusion, it is pointed out that^ it is 

 by no means possible to state definitely which is the 

 best of the "high explosives"; probably the most 

 powerful one in use is tetranitroaniline. It would^ be 

 extremely difficult to produce a substance having 

 greater explosive force than those already discovered 



NO. 2427, VOL. 97] 



and in use at the present day. Whether any advan- 

 tage would be gained by the discovery of explosives 

 which are more powerful than those already in use 

 is another matter. With "high explosives," once it 

 is possible to plant them on the exact spot at which it 

 is desired to effect destruction, such destruction can 

 be effected with as great completeness by the employ- 

 ment of one of the present-day "high explosives" as 

 with any new one which may be discovered. On 

 the other hand, any increase in the "safety" proper- 

 ties of "high explosives," and improvements in other 

 directions tending towards facilitating their trans- 

 port, would be a gain from a military point of view. 



R. L. Datta and N. R. Chatterjee have recently 



described (Journal of the American Chemical Society, 



37, No. 3) the action of aqua regia on acetone, ether, 



methyl, ethyl, and allyl alcohols, and formic and 



acetic acids, with the production of chloropicrin. The 



1 yield of the latter substance is almost quantitative in 



i the case of acetone and allyl alcohol when the reaction 



j mixture is warmed. It is stated that the following 



[ method of preparing chloropicrin is far preferable to 



I Hofmann's method in which bleaching pow-der is 



allowed to act on picric acid. To a mixture of two 



parts of nitric acid with three parts of hydrochloric 



acid, a quantity of acetone equal to one-tenth part of 



the acid mixture used is gradually added, the reaction 



mixture being warmed slightly. After heating on a 



water-bath to complete the reaction, the liquid is 



steam-distilled, the compound separated, dried over 



calcium chloride, and finally redistilled at a slightly 



reduced pressure. 



Messrs. George Ah.en and Unwin, Ltd., are pub- 

 lishing at an early date, for the Polish Information 

 Committee, pamphlets entitled "The Landmarks of 

 Polish History," "The Polish Question as an Inter- 

 national Problem," "An Outline of the History of 

 Polish Literature^" " National Music of Poland," and 

 "Poland as an Independent Economic Unit." Fur- 

 ther pamphlets, entitled "A Sketch of Polish Art," 

 "The Population of the Polish Commonwealth," 

 " Poland as a Geographical Individualit\-," and " In- 

 tellectual Poland," are in active preparation. 



OUR ASTRONOMICAL COLUMN. 



Variable Stars of Short Period. — Prof. E. C. 

 Pickering directs attention to some similarities and 

 peculiarities in the formulae representing the 

 light variations of the typical short-period variable 

 stars (Circular 190, Harvard College Observatory), not 

 only affording criteria for purposes of classification, 

 but also indicating structural features. It is found 

 that fi Lyrae should be regarded as intermediate be- 

 tween the Algol eclipse variables and the S Cephei 

 stars — exactly the order, it may be added, demanded 

 by Sir Norman Lockyer's meteoritic hypothesis. 



Photo-electric Photometry. — Prof. J. Stebbins 

 gives some details r^arding the employment in stellar 

 photometry of a specially sensitive rubidium cell (Lick 

 Observatory Bulletin, No. 277). This particular cell 

 is an outcome of some two years of conjoint research 

 with Prof. J. Kunz. The observational work was 

 carried out at Mount Hamilton, June 21-July 30 last 

 year, and several sets of measures are included for 

 nearly every day during the interval embracing three 

 cycles of the star's period. Important real irregulari- 

 ties are revealed, but the mean light curve has never- 

 theless been determined. The two maxima are found 

 to be practically equal. A marked asymmetry of the 

 light curve on each side primary minimum (the de- 

 crease of light being more rapid than the increase) is ex- 

 plained by an assumed non-uniform surface intensity 



