May io, 1900] 



NATURE 



31 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. "^ 



Note on some Red and Blue Pigments. 

 The following data are placed on record because interesting 

 in themselves, and in the hope that they may be useful to others 

 who have the opportunity to make further investigations. 



(1) A little boraginaceous plant called Eremocarya micrantha 

 (Torrey) is common in sandy places at Mesilla Park, New Mexico, 

 flowering in April. A few days ago, Prof. E. O. Wooton called 

 my attention to the fact that its roots are deep red, and stain 

 herbarium paper. Curious to learn more about this peculiar 

 coloration, I made some tests, with the following results : — The 

 pigment is not soluble in water, but it readily dissolves in cold 

 alcohol, forming a beautiful red solution. The roots, after being 

 treated with alcohol, become while, showing that the pigment is 

 entirely superficial, and is apparently an excretion from the root. 

 The red colour is that of the normal or acid state of the pigment, 

 but on adding enough liquor potassa; to make the solution alka- 

 line, the colour immediately becomes a beautiful blue. An ex- 

 cess of strong caustic potash does not destroy the pigment until 

 after a considerable time. Prof. A. Goss tested the delicacy of 

 the colour-reaction in the presence of acids and alkalis, and found 

 that a very small excess of one or the other would give the 

 characteristic colour. The pigment is, of course, an anthocyan, 

 very similar, at least, to litmus ; and it may be that it can be 

 utilised for the same purposes. 



(2) It has been remarked more than once that whereas the 

 hind wings of Acridiidre (grasshoppers) are sometimes blue, 

 sometimes red, and sometimes yellow, species living in the same 

 locality, though of very diverse genera, will often have similarly 

 coloured wings. In the Mesilla Valley we have common species 

 with red and with yellow wings ; but in the Organ Mountains, 

 not far away, I found two species very abundant, both having 

 blue wings, and otherwise coloured much alike, though of totally 

 different genera. These were Leprus wheeUri and a Trimero- 

 tropis which I took for T. cyanetpennis, but which Mr. S. H. 

 Scudder tells me is distinct and apparently undescribed. As the 

 blue of the wings appeared to be certainly a pigmentary colour, 

 and much resembled the vegetable anthocyans, I detached one 

 of the wings of Leprus wheeleri, and boiled it in dilute hydro- 

 chloric acid. As I had hoped, but hardly ventured to expect, 

 the blue at once became red. Heating the thus reddened wing 

 in liquor potassiE did not change it back to blue, but caused it to 

 turn yellow. I infer that the blue pigment has a red (acid) phase, 

 but that strong alkali will destroy it altogether, leaving a yellow 

 coloration which is of a different character. It is difficult to 

 avoid the conclusion that the redness or blueness of the wings in 

 these grasshoppers may result from the action of some environ- 

 mental factor (e.g. the juices of plants eaten) upon the pigment, 

 and that this accounts for the colour-similarity of diverse species 

 living at the same place. Of course, this is not supposed to 

 account for the similarity of the colours of the tegmina and 

 thorax, of which the various shades of grey, red and brown 

 resemble those of the rocks and ground. 



T. D. A. COCKERELL. 



Mesilla Park, New Mexico, U.S.A., April 17. 



Valve Motions of Engines. 

 In your number of December 14, 1899, Prof. John Perry men- 

 tions a dijigram by Mr. Harrison. This diagram is the same as 

 " Das biz*trische polare Exzenterschieberdiagramm " of F. A. 

 Brix in the Zeitschrtft des Vereins Deutscher Ingenieure, April 

 10, 1897. 



There is only a small difference, as Mr. Harrison finds the 



'iistance OC by means of a circle with radius = length of con- 



ccting-rod, and Mr. Brix finds that distance by calculating it 



R» 



at of -j-}(R = length of crank, L = length of connecting- 

 rod). Now OC has not exactly that value, but the fault made 

 therewith is much smaller than the fault made by describing 

 he circle. Therefore the method of Mr. Brix is preferable to 

 iiat of Mr. Harrison. F. J. Vaes. 



Rotterdam, April 14. 



NO. 1593, VOL. 62] 



Mr. Bri.k seems to have solved only the simple case of a 

 valve worked by an ordinary eccentric. There are other good 

 graphical solutions — for example, by Coste and Maniquet in a 

 modified form of the Reauleaux diagram, which gave accurate 

 results. Mr. Harrison's diagram is more general and is 

 applicable to link and radial valve-gears and to all motions 

 which are composed of a simple harmonic vibration with a small 

 octave superposed. It may be used for velocities and accelera- 

 tions as well as mere displacements. As to calculating the 



R'^ 

 distance OC by the formula rr-' instead of using the construc- 

 tion of the circular arc, this is a matter of no importance because 

 there is no appreciable difference in the answers. 



April 28. John Perry. 



Drunkenness and the Weather. 



I NOTICE in )our issue of March 15 a communicatioo from 

 Mr. R. C. T. Evans, of Gray's Inn-road, W.C, calling attention 

 to a probable error in my deductions in the paper which appeared 

 in your issue of February 15, under the title " Drunkenness 

 and the Weather." He says, " When a man is intoxicated and 

 commits an assault, the result is entered in the police reports as 

 ' assault,' the more serious offence overshadowing the less ; so 

 that in all probability many of the cases of assault referred to 

 in the statement were also cases of drunkenness, but were not 

 tabulated as such. Studying Prof. Dexter's curves in this light, 

 we may reasonably conclude that the number of those arrested 

 for drunkenness or its results, varies but little throughout the 

 year." 



Although his supposition seems a reasonable one, a fuller 

 statement of the conditions of the study will show that the 

 fluctuations of the "drunkenness" curve cannot be so easily 

 accounted for. 



First, the monthly occurrence of arrests for drunkenness for 

 New York City is more than twice that for assault, even in the 

 summer, when the former are at the minimum and the latter at 

 the maximum for the year, and if we suppose that every person 

 arrested for assault in the summer was also intoxicated and 

 would have come into the hands of the law for that crime if he 

 had not for the other, even this would not bring the drunkenness 

 curve up to its normal for the winter months.; 



Second, the method of recording crime by the New York 

 City Department of Police makes this practically impossible. 

 Misdemeanours are there classified and recorded under 183 

 different headings. The two which I have compared are 

 "assault and battery" and "intoxication." Therf^ are, how- 

 ever, four other classes of assault besides, one for "intoxication 

 and disorderly conduct," equalling that of "assault and 

 battery" in the annual number of arrests, besides one for 

 "fighting." A letter just received from the Clerk of Police 

 says, ""The crime of intoxication and fighting — a drunken 

 brawl —would be classified in the statistics as ' intoxication and 

 disorderly conduct.'" A careful analysis of all the conditions 

 would make it seem that only occasionally would arrests for 

 "assault and battery" encroach upon the data of drunkenness. 

 I believe they might sometimes do so, but not sufficiently often 

 to materially influence the curve. Edwin G. Dexter. 



Greeley, Colo., April 17. 



SOME SPECULATIONS AS TO THE PART 

 PLAYED BY CORPUSCLES IN PHYSICAL 

 PHENOMENA. 



IN some experiments described in the Phil. Mag. 

 October 1897, I showed that in the kathode rays 

 there were present bodies whose mass was exceedingly 

 small compared with the masses of ordinary atoms ; these 

 masses, which carry a charge of negative electricity, I 

 called "corpuscles." Ever since then I have indulged in 

 speculations as to the possibility of these corpuscles 

 existing in a free state in ordinary matter not under the 

 influence of the very intense electric field which are 

 associated with the kathode rays. As recent work has 

 produced some evidence of the free existence of these 

 corpuscles, I have thought that these speculations might 

 be of some interest to a wider circle than that to which 

 they have hitherto been addressed. In the Phil. Mag. 



