July 8, 1922] 



NA TURE 



45 



field within a horn or tube lined with an absorbent 

 substance. The transmission of sound through fabrics, 

 walls, and telephone booths may also be quickly 

 examined. The instrument is used by psychologists and 

 by telephone and acoustic engineers, and is of interest 

 to navigators. An interesting by-product is an instru- 

 ment for showing the direction of an acoustic signal 

 in the fog. It has been called a phonotrope, on the 

 analogy of heliotrope, which turns to the sun. It 

 consists of two equal horns which bring the sound to 

 the opposite sides of the disc. When the whistle 

 blows, the band of light spreads out, and on turning 

 the instrument it closes to zero when the sound is 

 directly ahead. Thus at several miles the direction 

 is given to within two or three degrees. 



Finally, let us consider that mystery of sound, 

 the violin, which has been studied by Prof. Barton 

 of Nottingham, and by Prof. Raman at Calcutta. 

 This may be described by the engineer as a box of 



curious shape, made of a curious substance, wood, of 

 variable thickness, with two holes of strange figure to 

 let the sound out of the resonating box. The latter is 

 actuated by a curious substance, catgut, made of the 

 intestines of a sheep, and set in vibration by another 

 curious substance, the tail of a horse. Yet from this 

 wonderful box we get- the most ravishing sounds, 

 which affect profoundly the emotions of the most 

 civilised. Yet the physicist reduces all musical 

 instruments to combinations of resonators with strings, 

 membranes, bars, plates, and horns. The mathematical 

 theory of strings was given by Euler two hundred years 

 ago, of bars and plates less than a hundred years, 

 of resonators by Helmholtz and Rayleigh, and I 

 have recently added a theory of horns which, while 

 only approximate, works well in practice, and investi- 

 gations are now being carried out by such methods on 

 vowels and the violin. 



Biological Studies in Madeira. 

 By Dr. Michael Grabham. 



'"["'HE component islands and rocks on the Madeira 



1 Archipelago are separate foci of volcanic ejecta 

 in the abysmal oceanic depths, and the level of 

 the Atlantic waters might be lowered ioo fathoms 

 without merging them in a common connexion. Of 

 the 170 forms of Testacea existing in the region, only 

 five species are distributed throughout the Island group, 

 and such evidence is adversely copious and conclusive 

 as to the theory that the Madeiras are a surviving relic 

 of a former continent. 



The fossil shells now lifted 1500 ft. above the sea 

 level show an upper Miocene association, but the 

 massive piling up of volcanic matter in countless 

 reiteration of eruption and age-long intermission began 

 long before the fossil shells were living creatures on a 

 Miocene shore. 



Examination of a fossil leaf-bed, containing examples 

 of the specific insular flora buried 120 ft. beneath a 

 variety of strata and capped by a thick deposit of 

 white trachyte, shows that the trachyte rock has 

 almost disappeared under the slowly working forces 

 of erosion and disintegration. Fr,om this is adduced 

 the enduring quality of the trachyte steps and gate- 

 ways of Funchal, which have been exposed for two 

 centuries, with little evidence of decay, to the same 

 influences under which the thick leaf-bed cap has 

 vanished. Thus we need set no niggardly limit to 

 the time requirement for the establishment of the 

 specialised forms of life developed and buried ages 

 before the trachyte capped the successive strata in a 

 flowing stream of lava. 



The Archipelago came to us 500 years ago, in the 

 dawn of navigation, ready made, already well worn 

 into characteristic scenery, with the local flora stabil- 

 ised, the discover}' being due to the erratic drifting 

 from its course to the West African coast of a crazy 

 vessel of Prince Henry the Navigator. An ancient 

 building is regarded locally as the traditional home 

 of Christopher Columbus, who married the Admiral 

 Peristrello's daughter, and was, no doubt, inspired for 



NO. 2749, VOL. I 10] 



his western enterprise by watching the sea currents 

 and the evidence they brought of land and life beyond 

 the horizon. 



The agencies of transport and distribution we know ; 

 the sea currents are the same ; the same winds prevail ; 

 the same birds come and go, though it may be difficult 

 to believe that the presence of the Testacea in 170 

 forms and the Coleoptera in 700 species has been due 

 to fitful and accidental influences. It is difficult, 

 though the rain falls now as formerly, to point to -a 

 single rock or ravine as having appreciably lessened 

 or deepened, though the storms of every winter carry 

 thousands of tons .of material to the ocean bed. 



The completeness with which the natural orders 

 exist in Madeira and the prevalence of specific forms 

 make it less bewildering to believe that these forms of 

 life were brought to us in pots from the Garden of 

 Eden than to trace their descent from primeval forms 

 which no longer survive. The shells can be compared 

 with fossilised ancient types, but the flora has-no such 

 satisfactory appeal. 



The name " Madeira " is derived from the hard 

 wood known as Materia ; Coniferae are not prominent 

 in the native flora. I have introduced Finns Insignis, 

 Cupressus Macrocarpa, and other species, while the 

 seeds of Persea Indica have been sent abroad with 

 the view of enlarging the range of the alligator pear- 

 tree by grafting. 



In conformity with other oceanic centres, Madeira 

 has numerous examples of orders with a single genus 

 and of genera with a single species. The striking 

 fruticose echiums illustrate stabilised specific forms, 

 and show how a new bee has effected an important 

 hybridisation by which perennial characters were 

 conferred on a plant of biennial life-limit, the helicoid 

 flowering cymes, normally t\ inches long, being pro- 

 longed into growths 7 or 8 feet high. 



The Carniolan bee concerned in this hybridisation 

 at first abstained from fruit eating, but it speedily 

 blended with the local black bee and became a vine- 



