722 



THE TROPICA!* AGRICULTURIST. 



[March 2, 1885. 



entale), Laurels (Calophvllum inophyelum), Palmyra 

 and Date Palms (Phrenix sylvestns) and many otbers 

 may be mentioned but none of them combine all the 

 advantages that the easuarina does, and none of them 

 would so well harmonize with the general appearance 

 of the coast. 



If rough mounds of sand be preferred to hide the 

 smooth, well trimmed slopes and sharply denned 

 angles " of the buttery, they must be fixed in situ 

 as suggested by Colonel McLeod by a covering of 

 sand binding plants, such as Ipomea pes-caprae, 

 Spinifex fquarrosus, Hydropbylax maritima, Micre- 

 chynehus sarmeutosus, Sesamura prostratum, or the 

 like ; but perhaps an objection to this plan might be 

 that to keep these plants thoroughly efficient in the 

 hot weather they would need attention, which would 

 make more or loss of a green spot, or oasis, easily dis- 

 tinguished From the sea. Probably it would be pre- 

 fc-rable, unless clipped casuarina be used for this pur- 

 pose also, to plant a broad belt of thorny shrubs such 

 as may be found growing in similar positions along 

 the coast. First among such shrubs may be named 

 the screw-pine (Pandanus odoratissimus), which as a 

 ragged screen witl» a most irregular outline, wou d 

 serve the purpose admirably, while sea-breezes would 

 to curb its rampantgrowth that little attention would 

 b? needed to keep it low. The screw-pine too has 

 the great merit of being very easily grown and trans- 

 planted, all that is required being to stick the tops 

 of branches into the sand at the. beginning of the 

 rains and they will root and spread without further 

 care. Amongst the sand-hills on the coast near Madras, 

 are to be found growing naturally many shrubs and 

 creepers which would excellently serve the required 

 purpose. The dwarf date Palm (Phieuix farmifera, 

 Koxb ) is verv common, forming dense masses of spines, 

 usually under nine feet high ; and with it flourish 

 abundantly other thorny shrubs of lower and weaker 

 growth, such as Grnelina asiatica, Canssaa carandas, 

 Onilandina honducella, Toddalia aculeata, Calamus sp., 

 Capparis horrida, Capparis divaricata, Zizyphus cenoptia 

 llugonia mystax, and Griffithia fiagrans. Many of 

 these shrubs con be easily grown from seed, as can 

 many others of thomless species which associate with 

 them but there might be much difficulty in getting 

 some of them as their roots ramble so far in the sand 

 that transplantation is next to impossible. 



For an entanglement nothing could better serve the 

 purpose than broad zones of the plants mentioned 

 above The following ideal obstruction would stop 

 even an elephant :— First a btlt of Agave vivipara 

 planted on low banks, row after row, then a ditch 

 with its bottom thickly planted with Calamus sp. 

 ( The wild rattan which commonly grows in such situ- 

 ations mar Madras). Next a few lines of plants and 

 s'iriib. iUch as (oorcapillay, dwarf date, Screw Pine, 

 Zz pliu< ceicplia, and Grnelina as'atifa, overgrown, 

 twisted, nn-1 hound together by the long thorny trailers 

 of Capparis hoirida (Juilandiua bouducella and Tod- 

 ila'ea aculoata ; and within alia den?e fringe of clipped 

 oisunrinaa behind which the defenders could unseen 

 a'-rai ge a wartn welcome for man or beast hardy 

 enough to face the thorns.— Madras Mail. 



THE GEOLOGY OF MADURA AND T1NNE- 

 VELLY. 



From an article in the Madras Mail reviewing a 

 paper by Mr. Foote of the Geological Department 

 we take a very interesting extract referring to the 

 formation of Adam's or Kama's Bridge between Ceylon 

 and India and the cuiious banks of red sand so 

 conspicuous in parts of tlio Madias Presidency and 

 also in Tiavaucore : — 



The chief geological interest, of course, lies outside 

 of the gneissic area on the strip of country, reaching 



from the coast line for a varying distance inland, which 

 is occupied by the more recent rocks. This area is 

 chiefly covered with gritty sandstoues belonging to the 

 Cuddalore beda, latentic conglomerates and alluvium, 

 but it also contains several small sub-recent marine 

 beds of limestones and grits, which are given in the 

 table as ''upraised coal reefs," but this, we fancy, 

 must be a misprint, for "coral reefs." Perhaps the 

 most interesiiug of these upraised coral reefs is one 

 which forms a striking feature of the north coast of the 

 island of Kameswaram anel apparently extends from 

 Pamban to Aiiangundu as a narrow strip, and then 

 widens out to the north-eastward to form the north- 

 ern lobe of the island. This northern lobe seems to 

 owe its existence entirely to the upraising of the coral, 

 which is here covered by only a thin coating of alluvium. 

 At present the reef rises above the water-level for at 

 least ten feet, thus showiug a considerable upheaval 

 of this part of the coast iu comparatively recent times, 

 This is a circumstance which ought not to be lost sight 

 of by the promoters of the scheme for cutting a ship 

 canal across Rameswaram, a scheme which Mr. Foote 

 unceremoniously speaks of as "wild." There is no 

 means of determining exactly when the upheaval took 

 place, but, as Mr. Foote suggests, it seems probable 

 that it was this upheaval which gave rise to the 

 formation of " Adam's Bridge," which according to 

 local tradition, once joined the islaud of Rameswaram to 

 terra Jirma on both sides, anel was breached about A.D. 

 1480 by a tremendous storm. When we consider that 

 plutonic agencies do not seem to be quite quiescent 

 even yet on this coast, it appears by no m<ans im- 

 probable that Adam's Bridge or Rama's Bridge, as the 

 Hindus call it, was formed suddenly by the action of 

 subterraneous forces, and the mythical tales regarding 

 its formation by an army of monkeys are easily ex- 

 plained. So too is its subsequent destruction by a 

 storm, which was facilitated by the system of jointing 

 which crosses the barrier nearly at right angles. 



A very marked feature of the surface geology of the 

 southern districts is produced by the so-called " ..Eolian 

 Formations," consisting of blown sands, ' teris ' and 

 coast dunes. Of these the teris are the most important, 

 and hitherto there has been some difficulty iu explain- 

 ing fully the mode of their formation. The solution of 

 the difficulty offered by Mr. Foote is very simple, but 

 quite satisfactory. During the prevalence of the South- 

 west monsoon heavy gales blow almost continuously for 

 mouths together. By these gabs great clouds of red 

 dust are swept up from the broad belt of loam which 

 skirts the eastern base of the ghats, and are carried 

 along eastward till they meet the sea-breezes near the 

 coast. The North-East monsoon would of course tend 

 to neutralize this action, but it is usually far less 

 violent thau the South-West one, and is accompanied 

 by heavy showers which tend to fix and consolidate 

 the blown saud. In fact the action is similar to what 

 we see going on, on the south side of tiiH Madras har- 

 bour, where, in spite of the counteracting influence of 

 the North-east nvusoou, the saud ii btiug steadily 

 heaped up against the breakwater. Some of the geo- 

 logical chaujjes produced by these teris;are very import- 

 ant. Thus Mr. Foote points out that there are several 

 fresh water lakes in South-east Tinnevclly which have 

 been formed solely by the damming back of the local 

 surface drainage by these hills of red sand. The most 

 important of these is the Taruvai lake, which is sur- 

 roundeel by these teris on three sides, and is lenlly a 

 natural lake, though entered in the district maps as a 

 tank with an artilicial bund. The view across this lake 

 which iu wet seasons forma a fiue sheet of peifectly 

 fresh water, is described as a very remaikahle one, 

 and possibly unique, the pure and intense red of 

 the foreground forming a bold contrast with the 

 green of the mid-distauce, and the varying 

 blue tints of the background and sky. Another 



