HA RD WICKE'S SCIENCE- G OS SIP. 



247 



substitute for the steam-engine. Instead of using 

 water, with its boiling-point of 212 , as a source of 

 vapour, he uses a volatile liquid which is convertible 

 into elastic vapour at a temperature easily obtained 

 by solar radiation, or at the ordinary temperature of 

 the air in summer. The engine is to be used for 

 raising water from wells where the water itself is cool 

 enough to condense this vapour. It is thus described 

 in "Iron :" — "The roof of a shed or small building is 

 made of tight compartments formed of iron plates, 

 which are rivetted at their edges. In each of the 

 compartments a volatile liquid is enclosed, which 

 becomes vapourized by the atmospheric heat, the 

 vapours escaping by tubes which meet in a common 

 reservoir. Whatever liquid is drawn with the gas, 

 returns to the compartments by a lower tube. The 

 vapour passes from the reservoir to a metallic sphere 

 at the bottom of the well. This sphere has a caout- 

 chouc diaphragm which can be fitted by its elasticity 

 alternately to the upper or lower hemisphere, so as to 

 move a sliding valve, and by the alternate introduc- 

 tion and condensation of the vapour to raise water 

 in considerable quantities." In actual working, a 

 machine of this kind raised 260 gallons of water per 

 hour from a depth of twenty-three feet. 



The Re-afforesting of London. — This subject 

 has been much discussed in some of the papers lately. 

 All agree in its desirability, but many despair of the 

 possibility of carrying it out. It is feared that the 

 trees in the proposed public avenues, and those 

 privately planted in back yards, will not survive the 

 London atmosphere. They certainly will not, if 

 planted without selection and discrimination. There 

 is one tree which has proved itself to be the Cockney 

 of the vegetable world, as it thrives in London as well 

 as, or even better than, anywhere else. Other trees 

 are suffocated by the particles of solid grime and the 

 coal-tar vapours that are so liberally diffused iu our 

 London atmosphere. The plane survives this by the 

 continual peeling of its bark. This peeling is visible 

 to everybody in passing ; the patches of new green 

 cuticle on the trunk and branches, and the old 

 exuvial bark lying at the foot of the tree, make it thus 

 obvious. I have examined these trees minutely, and 

 find a similar exfoliation extending to the fine twigs, 

 and suspect that even the leaves do something of the 

 kind, sufficiently to prevent the clogging , of their 

 stomata. A walk through the parks and squares 

 affords an interesting study of this subject. The elms, 

 the oaks, the conifera, and every other tree show 

 signs of premature decrepitude more or less marked 

 (less in the limes), while the plane flourishes 

 luxuriantly, no matter how near to reeking chimney- 

 pots. Therefore plant the plane at once, and in the 

 meantime let our official botanists at Kew, etc., look 

 out for other trees with similar self-cleansing pro- 

 perties and test them accordingly. If they ask for a 

 locality where the trial shall be desperately severe, I 



reply, The Wicker, Snig Hill, Saville Street, and 

 Carlisle Street, Sheffield. 



Drying up of Lakes. — It appears from the 

 Proceedings of the Geographical Society of St. 

 Petersburg, that some of the great lakes in the 

 Aral- Caspian region, especially those lying between 

 Omsk and Tomsk, or between the Aral and the 

 Obi, are rapidly drying. There is a group of three 

 large lakes, Chani, Soomwi, and Abychkan, with a 

 smaller lake, Moloki, between. The largest, Lake 

 Chani, has diminished considerably, and still greater 

 changes have occurred in the other lakes since reliable 

 maps have been made. Villages now occupy part of 

 the former site of Lake Moloki, which has contracted 

 to less than a fourth of its former dimensions during 

 the present century. Lake Abychkan has been 

 reduced in the same period from an area of 530 square 

 miles to three ponds, the largest being hardly a mile 

 and a half wide. Twenty-five years ago there were 

 several lakes, about ten miles long and eight wide, where 

 there are now only small ponds. Lake Tchebakly, 

 which in a map made in 1784 was shown as an oval 

 forty miles long and thirty wide, is shown in a map 

 of the beginning of this century as an irregular lake 

 still forty miles long, but reduced to a width of seven 

 to twenty miles, with several smaller lakes indicating 

 its former dimensions. Thirty years later the whole 

 was reduced to a few small lakes, the largest about 

 three miles in length and width, and now all that 

 remains of a lake which a hundred years ago had an 

 area of 350 square miles are three ponds. If we could 

 go further back to still earlier maps, we should doubt- 

 less find an inland sea, another Aral or Caspian, 

 occupying the site of all these lakes and a considerable 

 distance around. Lacking the maps we have geological 

 evidence quite as reliable, though not so striking. 



Centenarians. — The cases of Sir Moses Monte- 

 fiore and Chevreul have refuted the scepticism con- 

 cerning the existence of centenarians which had lately 

 come into fashion. It was easy to deny the claims 

 of the rustic patriarch, but those of two men who 

 have been before the world with so much distinction 

 cannot be set aside. Many other instances, recently 

 assumed to be fictitious, are now regarded very 

 differently. I do not go so far as to claim implicit 

 reliance on the assertions of the Irish Countess of 

 Desmond, second wife of the 12th Earl of Desmond, 

 and married to him in 1530. She was seen by Sir 

 Walter Raleigh in 1589, having already presented 

 herself to the English court claiming the age of 140. 

 She came to an untimely end in 1604 by falling from 

 a high branch of a cherry-tree planted by Sir Walter 

 Raleigh. According to the family traditions she was 

 162 years of age, and had recently cut her third set 

 of teeth. The cherry-tree was introduced to Britain 

 by Sir Walter Raleigh, and that which the old lady 

 was climbing so skittishly was one of his first plantings 



