246 



NATURE 



\_July 13, 1882 



"Megaceros Hibernicus" in Peat 



My friend, Dr. Leith Adams, has given it as his opinion that 

 the Irish elk is only found in the clay or marl under the peat, 

 while I contended that some of them occur in the peat, this 

 opinion being formed from reports of finds in the counties of 

 Limerick, Carlow, and Wexford, also from the colour and 

 appearance of the bones ; still I could not be positive, as I had 

 not myself seen the bones raised out of the peat. Last week, 

 however, I heard from Capt. Woodrift, Kilovven Inch, Co. 

 Wexford, that he had found an elk's head in the peat, and I 

 went to see it. It was lying on its back altogether in the peat, 

 except some of the points of the horns. The portions in the 

 clay under the peat were quite hard, while those in the peat were 

 soft, but became quite hard a short time after they were taken 

 out. 



The "Elk Hole" at Kilowen is a very remarkable place, 

 because, although very small, not 203 yards in diameter, yet at 

 the present time the remains of over ten skeletons of elks have 

 been taken out of it ; while in the undi-turbed portion of the 

 bog there are probably other skeletons. A few miles to the 

 south-west of Kilowen there is the small bog of Axe, in which 

 the remains of the C. megaceros has also been found. 



Ovoca, July S G. H. Kinahan 



Perception of Colour 

 Happening to be reading out of door-, while the sun was 

 shining on my book, I noticed that patches of weed on the lawn 

 appeared peculiarly conspicuous in their difference of tint from 

 the grass- The same patches of weed close-cropped to the level 

 of the grass were ordinarily scarcely observable from difference 

 of colour. Now, as I looked up from my book — my eyes 

 dazzled with the glare — they appeared to me to have a strong 

 blue tint. My attention thus being drawn to the point, I ex- 

 tended my observations, with the following results, which, if 

 new, will doubtless prove interesting to some of your readers. 

 I found that if the eye was exposed for two or three minutes to 

 the action of a very strong light, by looking at a sheet 0/ while 

 fapa-, while bright sunshine fell on it, the capacity of the eye 

 for perception of colour was curiously modified, under certain 

 conditions. For example : if, on the instant afier the expo.-ure 

 of the eye to strong light, as described — solarisation I will call 

 it — flowers of various colours, placed in a shady part of a room 

 were examined, a pink rose appeared the colour of lavender ; 

 dark crimson Sweet William, almost black ; magenta Snap- 

 dragon, indigo ; scarlet Poppy, orange ; the eye was, in fact, 

 red-blind. After a minute or two, the eye recovered its normal 

 sensibility to red, and the flowers assumed their natural colour. 



In order to ascertain that the mal-perception of colour, under 

 the conditions described, was due to the action of strong light 

 on the eye, and not to any other circumstance, I repeated the 

 experiment, allowing the solarisation to take place on one eye 

 only, the other eye being kept shut until the moment of making 

 the observation. I then found, as before, that the solarised eye 

 was red-blind to objects in a subdued light for a minute or two 

 after solarisation, but sensitive to blue, and in less degree to 

 yellow, while the non-solarised eye was perfectly normal in its 

 perception of all the colours. By alternately closing and open- 

 ing the solarised and non-solarised eye, the difference in colours 

 perceived by the two eyes was extremely striking — the rose was, 

 as seen by one eye, pink, by the other eye, blue. It must be 

 remembered that the effects described were produced when the 

 flowers were observed in a room not strongly lighted. 



When a corresponding experiment was made with the flowers 

 in the sunshine instead of in the shade, it was found that 

 a reverse effect was produced — that every colour, and red 

 particular, was intenser to the solarised eye than to the non- 

 solarised eye— as was readily seen by alternately shutting and 

 opening them. To the solarised eye a red rose-bud was deep 

 red, to the other, eye light red. The red of the poppy was 

 deeper and more vivid to the solarised eye. A calceolaria 

 was orange chrome to the solarised eye, lemon chrome to the 

 non-solarised eye. A viola was dark violet to the solarised 

 eye, a colder tone of blue to the non-solarised eye. 



I found that after the insensibility to dimly lighted red and 

 orange (the effect of solarisation) had worn off, a reverse condi- 

 tion succeeded, for example, Venetian red, w hich was a dirty 

 brown, as seen the instant after solarisation, appeared gradually 

 to change to a full vermillion. I found also that portions of the 

 solarised eye that had escaped the solarising acti jn behaved like 



the non-solarised eye. I leave the explanation of these slight 

 observations to those within whose special field of study they 

 naturally falL only remarking that the power of the eye, 

 fatigued by solarisation to perceive blue light, and light of no 

 other colour, under the conditions described, seems to suggest 

 that the eye, like almost all matter sensitive to light, is more 

 sensitive to blue rays than rays of lower refrangibility. 



Lancing, July 10 J. W. Swan 



WATER-JET PROPELLERS 



VERY early in the history of steam navigation, 

 attempts were made to employ the "hydraulic" or 

 "water-jet" propeller. About 1782 Rumsey began to 

 work in this direction, using a steam-engine to force water 

 out at the stern of a boat, the inlet being at the bow. His 

 experiments are said to have extended over twenty years, 

 but led to no practical result. Another American, named 

 Livingston, applied the same principle of propulsion in a 

 different manner. A horizontal wheel, or turbine, was 

 placed in the bottom of the boat, near the middle of the 

 length, the water was admitted from beneath it, and 

 expelled from the periphery of the wheel through an 

 opening at the after part of the boat. In 1798 a monopoly 

 was granted to Livingston for twenty years by the State 

 of New York, on condition that within a given period he 

 produced a vessel capable of attaining the speed of four 

 miles an hour- This condition was not fulfilled, and, as 

 is well known, the first successful steamers built in this 

 country or abroad were propelled by paddle wheels. This 

 form of propeller alone was employed for nearly forty 

 years, during which period steam-ships increased greatly 

 in numbers, size, and speed, proving themselves well 

 adapted not merely for service on inland and coasting 

 navigation, but also for ocean voyages. Just when the 

 Transatlantic steam service had been successfully com- 

 menced by the Great Western and Sirius, both paddle 

 steamers, the screw-propeller began to threaten the 

 supremacy of the paddle-wheel ; and the success of the 

 Archimedes in 1840 led to the adoption of the screw in the 

 Great Britain, as well as the construction of the screw 

 sloop Rattler for the Royal Navy. Soon after came a 

 revival of the water-jet propeller by the Messrs. Ruthven 

 of Edinburgh. In 1S43 their first vessel was tried, attain- 

 ing a speed of about seven miles an hour. Ten years 

 later a fishing-vessel was built on the same principle, and 

 exceeded nine miles an hour. Several other river steamers 

 and small craft were constructed with jet-propellers in the 

 period 1853-65, but they were all comparatively slow, and 

 the plan did not grow into favour either as a substitute 

 for the paddle-wheel or the screw. 



There were certain features in the jet-propeller which 

 recommended it to the judgment of many naval officers 

 who had witnessed the trials of vessels so fitted ; their 

 influence led the Admiralty in 1S65 to order the construc- 

 tion of a small armoured vessel, appropriately named the 

 Watemvitch, which was to be fitted with Ruthven' s pro- 

 peller. Admiral Sir George Eliot was one of the principal 

 advocates of a trial of the new system, in which he has 

 always continued to take a great interest. In the German 

 navy, trials of the Ruthven system have also been made 

 on a small vessel named the Rival, and experiments of a 

 similar nature have been made in Sweden. At the present 

 time Messrs. Thornycroft are building for the Admiralty 

 a torpedo-boat, to be propelled by water-jets, the trials of 

 which are awaited with interest, since the)' will furnish 

 another comparison between the performances of the 

 hydraulic propeller and the screw. 



The Ruthven system agrees in its main features with 

 the proposal made by Livingston forty years earlier. As 

 an example the arrangements of the Water-witch may be 

 briefly described. Openings are made in the bottom of 

 the ship amidships, to admit the water into a powerful 

 centrifugal pump or turbine, the axis of which is vertical. 



