Oct. II, 1877] 



NATURE 



509 



crease in the size of the flowers and the loss of pollen. With 

 the loss of pollen the whole machinery of the two-armed 

 levers, which had been so gradually acquired and so 

 exactly brought the pollen on the back of the visiting 

 humble-bees, has become useless and begun to abort, 

 and, according to its new origin, this last abortion, as is 

 shown by Figs. 123-129, still offers various gradations 

 from the perfect mechanism to an insignificant little flap. 

 In this gradual succession of more and moie reduced 

 stamens of Salvia pratciisis, we find some forms (Figs. 

 125, 126) with a striking resemblance to the stamens of 

 Salvia officinalis (Fig. 130), and some of the steps which 



Fitjiso 



Fig. 130. — Salvia officinalis. Flower of Salvia officinalis bisected 

 longitudinally. 



are run through by this process of abortion seem to be 

 quite analogous to those by which in former periods the 

 stamens of Salvia pratc^iisis have reached their astonish- 

 ing singularity. 



Briefly, the original five stamens of the flower have 

 aborted at the following four successive periods : — 



1. The uppermost stamen, in the ancestors of the 

 family Labiats (complete disappearance). 



2. The two upper lateral stamens, in the ancestors of 

 the genus Salvia (reduction to little knobs). 



3. The two lower anther-cells of the two lower stamens, 

 beginning to abort in Salvia officinalis ; abortion and 

 metamorphosis perfected in .S". pratcnsis. 



4. The two upper anther-cells of the two lower stamens, 

 in the small-flowered plants of S. pratcnsis (abortion of 

 the pollen perfected, abortion of the anther-cells and the 

 whole stamens beginning). Hermann Muller 



Lippstadt 



THE RESTORATION OF THE ANCIENT 

 SYSTEM OF TANK IRRIGATION IN CEYLON 

 A WORK apparently pregnant with the largest and 

 -^~*- most beneficent results to the native population of 

 Ceylon is in process of being carried out by the Colonial 

 Government of that island. More than a thousand years 

 ago a system of irrigation, the most complete and remark- 

 able that the world has ever seen was in successftil opera- 

 tion in the Low Country, and the object which the 

 Government has in view is to restore to something like 

 its pristine fertility a large proportion of the immense 

 tracts of land — many hundreds of thousands of acres in 

 e.xtent — that for want of water have fallen into a condition 

 of the most utter sterility. Sir Emerson Tennant, writing 

 twenty years ago on this subject, says, " The difficulties 

 attendant on any attempt to bring back cultivation by the 

 repair of the tanks are too apparent to escape notice. 

 The system to be restored was the growth of 1,000 years 

 of freedom, which a brief interval of anarchy sufficed to 

 destroy, and it would require the lapse of long periods to 

 reproduce the population and recreate the wealth in cattle 

 and manual labour essential to realise again the agricul- 

 tural prosperity which prevailed under the Smghalese 

 dynasties. But the experiment is worthy of the beneficent 

 rule of the British Crown under whose auspices the 

 ancient organisation may be restored amongst the native 

 Singhalese." 



The origin of the system of irrigation spoken of dates 

 as' far back as the year 504 B.C., when, according to the 

 Singhalese Chronicle, Mahawanso, the first tank was 

 built in the neighbourhood of his new capital, Anuradha- 

 poora, by Panduwasa, the second of the Hindu Kings. 



This was succeeded about seventy years later by two 

 others formed in the same neighbourhood. In the year 

 459 A.D. the Kalawewe Tank, the largest of all, was com- 

 pleted. The retaining bund of this immense sheet of 

 water is twelve miles long, and the circumference of the 

 lake which it formed was no less than forty miles, the 

 water being backed up for a distance of fifteen miles and 

 conducted from the tank by means of a conduit sixty 

 miles in length to the capital. Sir Emerson Tennant in 

 describing these remarkable reservoirs, says, " Excepting 

 the exaggerated dimensions of Lake Mceris in Central 

 Egypt, which is not an artificial lake, and the mysterious 

 basin of Al Aram in Arabia, no similar constructions 

 formed by any race whether ancient or modern e.xceed in 

 colossal magnitude the stupendous tanks of Ceylon." The 

 same author estimates that at the time of its greatest 

 prosperity the island contained a population of from 

 fifteen to twenty millions, nearly all of whom must have 

 derived their means of sustenance from irrigated lands. 

 At the present moment, after all the care bestowed 

 through three-quarters of a century by a paternal govern- 

 ment, the population only amounts to 2,400,000, whilst even 

 for this a large proportion of the food— 6,000,000 bushels 

 of rice annually among other things — has to be imported 

 from India, and the population itself must be considered 

 to have been somewhat unnaturally increased during the 

 last fifty years by the stimulus of European enterprise. 

 The mass of the people too have changed their place of 

 residence from the interior to the neighbourhood of the 

 sea-coast, where trading and fishing instead of rice-culti- 

 vation furnish them a livelihood. The vast areas which 

 formerly under the magic influence of a sufficient supply 

 of water and a hot sun, produced their two or three crops 

 of rice in a year are now absolutely deserted, frequently 

 not a single inhabitant surviving where once a thousand 

 found ample means of subsistence. The city of Anarad- 

 hapoora, if its ruins afford us any means of estimating 

 its magnitude, must have covered an immense area — no 

 less than from thirty to forty square miles, and the popu- 

 lation living on the spot and drawing its supplies of food 

 from the immediate neighbourhood must have been corre- 

 spondingly immense. Now it is a mere village in the 

 midst of vast heaps of ruins. 



One of the most gigantic of these early irrigation works 

 is supposed to have been originated by IVIaha Sen about 

 the year 275 a.d., and, having been enlarged by Prakrama, 

 Bahul., who reigned in 1 153, to have received from him the 

 name of " The Sea of Prakrama." It consisted of a series 

 of lakes formed by an embankment twenty-four miles in 

 length and from forty to ninety feet high, by which the 

 water of a large river and many considerable streams was 

 hemmed in along the base of a range of hills and so 

 forced into the valleys that a series of lagoons or lakes 

 was formed extending for the above-mentioned distance 

 and frequently several miles in width. A canal five miles 

 in length conducted the waters of "the sea" to the Minery 

 Lake, another of the works of Maha Sen, to be mentioned 

 presently, and a further canal from Mmery led the waters 

 to the neighbourhood of Trincomalie, in all a distance of 

 fifty-seven miles. When it is remembered how sudden 

 and torrential the rains are in a country like Ceylon— the 

 writer has known 18 inches of rainfall in forty-eight hours 

 over a very large extent of country, and at one spot as 

 much as iS'9 inches in twenty-four hours, — we cannot 

 too much admire the vastness of such a work and the 

 skill which enabled the native engineers to use the 

 natural features of the country in such a manner that for 

 a distance of twenty-four miles a single embankment 

 sufficed not only to hem in the water for purposes of 

 irrigation but also to provide a vifater-way for the trans- 

 port of produce and merchandise. Along the whole 

 course of this embankment and canal and wherever its 

 tributaries carried the life-giving water there would be 

 without doubt a teeming population ; for irrigable land in 



