MECHANICS AND USEFUL ARTS. 67 



mercurial surface, and the means he used were planting it with the 

 piiia.-iter. Tii a report of his proceedings, which he, published, In- 

 compared this sandy tra-'t to a billowy sea, it offered nothing to the 

 eye but a monotonous repetition of white wavy hillock*; peifrctly des- 

 titute of vegetation. When violent storms of wind occurred, the sur- 

 face of these downs was entirely changed; what were hills had become 

 valleys, and valleys hills. The sand on these occasions was <>t'i"ii 

 blown into the interior of the country, actually covering culhvaied 

 fields, villages, and even entire forests. This was done so gradu:i ; !v, 

 in a shower of particles as fine as the sand used for hour-glasses, ih it 

 nothing was destroyed. The sand gradually rose among the crop.;, 

 as if they were inundated with water, and the herbage and the 1 :>;>; 

 of trees appeared quite green and healthy, even to the moment- of 

 their being submerged. On this moving and shifting sea, M. Bremon- 

 tier sowed seeds of the common broom, mixed with those of the pin- 

 aster ; commencing on the side next the sea, or on that from which 

 the wind generally prevailed, and sowing in narrow zones, in a direc- 

 tion at right angles to that of the wind. The first zone was protected 

 by a line of hurdles, and after it was established it protected the 

 second, as the second did the third, and so on. To prevent the seed 

 being blown away before it had germinated and become firmly rooted, 

 he protected it by various- ingenious modes, such as hurdles and 

 thatching, and he had at last the gratification, after conquering many 

 difficulties, of seeing his first zones firmly established. The rest was 

 then comparatively easy ; and by degrees the tree covered the whole 

 of these sandy downs, not only providing the interior country with a 

 barrier against the incursion of the sands, but turning the downs 

 themselves from a desolate waste into a source of productive industry. 

 Although the timber is of little value, the manufacture of tar, turpen- 

 tine, and other resinous products furnishes sufficient occupation for the 

 inhabitants who are thinly scattered over large spaces. Among the 

 efforts of man to control the elements and the powers of nature, the 

 conquest of the Landes from the desolation of the desert is entitled to 

 a place beside the recovery of Holland from the empire of the sea. 



FLOW OF WATER THROUGH IRREGULAR TUBES. 

 At a recent meeting of the !N". Y. Polytechnic Association, Mr. J. 



^J V 



B. Root explained an experiment made by him in relation to the 

 flow of water through irregular tubes. He constructed a tube of tin 

 30 inches long, and 2J inches in diameter. Within this tube were 

 soldered 11 diaphragms or discs, at regular distances from each other. 

 In each circular disc, there was a hole | of an inch in diameter, 

 the center of which was the center of the disc. Half-way from 

 each disc the tube was perforated on the upper side by a very small 

 hole. One end of this tube was inserted into a bulkhead about nine 

 feet below the surface of the water. The object of this apparatus 

 was to measure the retardation of the water, in passing through the 

 discs, by means of the height of the jets sent through the small holes 

 on the top of the tube. The jet from the first hole was about two 

 feet high ; the next jet was lower, and so on to the last hole, from 

 which the water barely oozed out. The rate in decrease in height 

 was directly as the number of discs inserted that is, the water 



