NATURE 



[September 2, 1915 



the author goes on to say that "it follows" that 

 the electrostatic unit = 3x101*' A.E.M.U.'s of 

 E.M.F. =300 volts. It would be a phenomenal 

 beginner who was able to follow this reasoning 

 without further explanation. A. Russell. 



OVR BOOKSHELF. 



Overcrowding and Defective Housing in the Rural 

 Districts. By Dr. H. B. Bashore. Pp. 92. 



(New York : J. Wiley and Sons, Inc. ; London : 



Chapman and Hall, Ltd., 1915.) Price 45. 6d. 



net. 

 We are apt to associate overcrowding and defec- 

 tive housing with towns in the *' old " countries, 

 but it is well to realise that a condition of things 

 as bad or worse may exist in our rural districts 

 and in new settlements. In this little book Dr. 

 Harvey Bashore, an inspector in the Pennsylvania 

 Department of Health, describes conditions of 

 overcrowding and defective housing which exist 

 in his own district. He deals with the subject 

 under four headings: (i) land overcrowding; (2) 

 house overcrowding; (3) defective buildings; and 

 (4) overcrowded and defective schools. 



Instances of these various conditions, illustrated 

 by well-reproduced plates, are given, and the 

 results are summarised in a concluding chapter. 

 The latter are exactly the same as in the great 

 cities — lack of efficiency, disease, and premature 

 disease to many — "while the great majority of 

 people subjected to overcrowding and bad housing 

 do not prematurely die, yet they have a lessened 

 physical and mental vigour and are less able to 

 do properly their daily work, and not only become 

 a loss to themselves and their families, but to the 

 State ; and for ever stand on the threshold of that 

 dread disease — tuberculosis; for tuberculosis is 

 the one great disease of the overcrowded." As 

 regards the remedy. Dr. Bashore says : " This 

 problem cannot be attacked, as in the great cities, 

 by legislative enactment or resort to legal mea- 

 sures, but the solution lies in proper education by 

 the health authorities, by the schools, and by the 

 Press, and the crusade must be kept up until the 

 people understand that it pays — pays in real 

 dollars and cents — to live in sanitary homes." 



Although written from the American view-point, 

 we would commend this little book to the notice 

 of councillors, landlords, and health visitors in 

 this country. R. T. Hewlett. 



Typical Flies. A Photographic Atlas of Diptera, 



including Aphaniptera. By E. K. Pearce. 



Pp. xii + 47. (Cambridge : At the University 



Press, 1915.) Price 55. net. 

 This volume contains four pages of introduction, 

 with instructions for collecting and for setting 

 specimens of flies caught, Brauer's Classification 

 of Diptera (four pages), and 155 reproductions in 

 half-tone of photographs of fleas and flies. Its 

 aim is to be of service to the beginner and to 

 draw attention to the interest of an order of insect 

 that is much neglected. 



The photographs are as good as any we have 

 seen of this class of insect — a peculiarly difficult 

 NO. 2392, VOL. 96] 



class to represent pictorially in any natural 

 manner ; the venation of the wings is well brought 

 out wherever the banding or colouring of the 

 wings does not obscure it, and there are excellent 

 short notes as to habitat, larval habits, and so on 

 under the pictures. We wish it had been possible 

 to provide under the photographs line drawings 

 of the more important types of venation and. of 

 some of the antennae ; but the interest taken in this 

 group is so little that we imagine further expendi- 

 ture on the volume was impossible. 



The diversity of appearance is well brought 

 out; to the student the venation systems depicted 

 will be helpful, and to the beginner the variety of 

 habitat and habit will be distinctly stimulating. 



Probably no order of insect will so well repay 

 the collector and investigator in this country, and 

 we hope this volume may stimulate a wider 

 interest in this fascinating group. H. M.-L. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for 

 opinions expressed 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.] 



Destruction of Wasps. 



You may be interested to know that whilst starting 

 up a motor-cycle a few days since, I accidentally 

 discovered that benzol sprayed over a wasp instantly 

 killed it. I tried the same experiment with petrol 

 with the same result. 



Knowing of two nests in the neighbourhood I went 

 that night and with a small oil gun injected two 

 or three ounces of benzol into each nest. In the 

 morning I found the two nests entirely destroyed. 



Next night I visited an open nest which had been 

 partly destroyed by another means, and in which 

 several hundred wasps were still living. They covered 

 an area as large as a cheese plate, and on lighting 

 them up showed signs of activity. One squirt full of 

 petrol was hastily sprayed over them, and the whole 

 lot were instantly killed. 



This method is so safe, simple, and effective that I 

 feel it should be generally known. The petrol or 

 benzol acts entirely by vaporisation and produces 

 asphyxiation. It is not fired in any way. 



A. H. Mitchell. 



Horn's Green, Knockholt, Kent, August 24. 



Atlantic Oceanic Currents. 



A LARGE bell-buoy was cast ashore at Porto Santo, 

 the northern island of the Madeira group, in the 

 early days of March in the present year. 



I have ascertained that the buoy came from Pearl 

 Reef, Magdalen Islands, in the Gulf of St. Lawrence, 

 having broken adrift from its moorings in the autumn 

 of 1912, occupying thus two years and a half in 

 transit. These facts are important at a time when 

 our accepted notions of the strength and direction of 

 the Atlantic currents are undergoing revision. 



It may be remembered that Christopher Columbus, 

 who resided at Porto Santo, and married a daughter 

 of Peristrello, the Governor in those davs, derived his 

 inspiration and dream of lands beyond the sunset from 

 the arrival of seed-pods and other suggestive matter 

 drifting in upon the broad current which bathes these 

 rocky shores. Michael C. Grabham. 



Madeira, August 19. 



