()k(,.\ \S ( il' A Nd roM-.CTID. 455 



!uni, as shown in llic tigurc, foi'iii ihc water-seal o\uv the swerv- 

 in,2^ part of the channel. 



The mechanism for obtainint^ air and for sealing the open- 

 ing;-, at the caudal end of the animal, appeared verv clearlx in my 

 material. 1 he wings extend a short distance beyond the li]) of 

 the abdomen. in life they are the only parts whicli project 

 abo\e the surface when the animal hangs head dow nwards. I hey 

 are at this point closely ai)])ressed to the abdomen. 1 therefore 

 l)elie\-e that no air enters the reserxoir l)eneath them at this 

 point. The hairs on the keel and the i)leurite. jmlled outwards 

 by the surface tension of the water as (listnr])e(l when the wing- 

 tips emerge. lea\e ])etween them two hole>, one for each channel, 

 ihrough which air enters. 



The sealing of the oi)enings takes place autoniaticalb' when 

 the animal leaves the surface. 'I'here i- no more surface tension 

 to hold the hairs ai)art. They are elastic and fly back to their 

 natural position tiat against the body, closing the air-channel. 



It will be noted that only one of the tufts of hair is on the 

 keel ; the other two are on the plein-ite on each side. My b'igure 2 

 shows in a diagrammatic \\a\- the arrangement of i)arts at the 

 end of the abdomen, 'ihe two channels and the keel, as well as 

 the tufts (..f hair, appear clearlw The abl)re\iations are the 

 same as in the other figui"e. 



1 have dissected the internal breathing organs of this 

 animal, and find nothing unusual to report. The tracheation is 

 exactly as in most other 1 lemiptera. The usual principal tracheic 

 are there, and without modifications ot' an\- sort. 



{ Read. July 6. 1917.) 



'RA\S.\C"'l"i()XS ()!•■ .soc !!•: ri''S. 



.Siirni Aku!c.\x S()cn-:Tv (U- (.'i\ii, F.m.i xki-jo. — i'rui'. A. !•'.. .Snajjc. 

 15. Sc. M.I.C.E.. I'rist President, in the rliair. — " So/isbi'ry [Soiillicni 

 Rhodi'sia) zvatcr -lyorks" : Pruf. R. II. Charters. .\ detailed description 

 1)1 various features (^f the works was i^iven, under the heads of Slora.tie 

 Reservoir, h'ilters. Gravitation Main. Service Reservoir. Higli-level 'I'ank. 

 and Distrihution Svsteni. 'I he entire cost of the works was i58..?04. — 

 " l.isscs in diiiiis by ubsorf^tioi: in inUind siih-tropical .if ricii " : A. il. 

 Wallis. The author submitted sucli evidence as wa.s av.-iihihlc to show 

 tlial the region referred to has heen gra(hiall_\ lieconiing more arid, and 

 urged tliat efforts should be made to retain in the country, hy the construc- 

 tion of dams, the large .f|uantities of rain that ultimatch run unconscrved 

 to the sea. The author proceeded to discuss the losses sustaineil li\ 

 dams through evaporation and percolation. — " Snnir rxi^criincnfs on the 

 rate of czaporalion of zi-ater tinongli films d' nil": Dr. J. R. Sutton. 

 The experiments were undertaken in order lo test the validity of the 

 suggestion that has l)ecn made <^>v. \arious occasions t'.iat tlie enorm(^us 

 loss by evaporation from Soui.'; African, waters might be sto])ped I»v 

 keeping a lilm of oil on the surface of the water. It appeared that at best 

 one gallon of kerosene would save no inore than 100 gallons of water, 

 and as on the table-land of South .Africa one gallon of kerosene is worth 

 500 to 1,000 gallons of water, it would not pay to use oil for the purpose 

 of retarding evaporation. I'rom a pliysical point of view there is consider- 

 able interest in tiie fact that water can eva!)orate through a skin of oil 

 as much as .02 of an inch thick. The oil nrobalily acts as a sort of 

 ' irah.im's membrane. 



