724 



RESEARCHES AND EXPERIMENTS. 



their lives are. Thus the proximity of people 

 in 53 districts is 147 yards, and there the mean 

 duration of life is 51 years; in 345 districts the 

 proximity is 139 yards, and the mean duration 

 of life 45 years; in 137 districts the proximity 

 is 97 yards, and the mean duration of life is 

 40 years ; in 47 districts the proximity is 46 

 yards, and the mean duration of life is 35 years ; 

 in 9 districts the proximity is 28 yards, and the 

 mean duration of life is 32 years. In Manches- 

 ter district the proximity is 17 yards, and the 

 mean duration of life is 29 years ; in Liverpool 

 district the proximity is 7 yards, and the mean 

 duration of lite is 26 years. This is a determined 

 law, and the duration of life being given in one 

 set of conditions, the duration of life in another 

 set of conditions is determined from the prox- 

 imities. 



Steering Great Steamships. Within a year 

 or two there have been several disasters to 

 iron-clad ships of war and other vessels pro- 

 pelled by screws, caused by the difficulty of 

 promptly controlling the movements of such 

 vessels by the steering apparatus, especially 

 when the screw is reversed or the vessel is 

 moving slowly. The subject was deemed of 

 sufficient importance to call for an investiga- 

 tion at the hands of a committee of the British 

 Association, and accordingly a number of very 

 distinguished members were commissioned to 

 make an inquiry. From their experiments it 

 appears that the distance required by a screw 

 steamer to bring herself to rest from full speed 

 by the reversal of her screw is independent, or 

 nearly so, of the power of the engines, but de- 

 pends on the size and build of the ship. On 

 the average such a vessel can not be brought 

 to a stop in less than from four to six lengths 

 of her hull. The main object of the Commit- 

 tee was to ascertain how far reversing the screw 

 did or did not interfere with the rudder's ac- 

 tion during the process of stopping. It was 

 found to be an invariable rule that during this 

 interval of stopping by reversal of the screw, 

 the rudder produces none of its usual effects to 

 turn the ship, but that its effect is then to turn 

 the ship in the opposite direction from that in 

 which she would turn were the screw going 

 ahead. In the mean time the vessel is at the 

 mercy of any other influence that may act 

 upon her. Thus the wind may, when the screw 

 is reversed, cause the ship to turn in a direc- 

 tion the very opposite of that which is desired. 

 Also, the reversed screw will exercise an influ- 

 ence, which increases as the ship's speed is 

 lessened, to turn her to starboard or port, this 

 being particularly the case if the ship is light 

 in draught. In no case has a ship tried by the 

 Committee been able to turn with the screw 

 reversed on a circle of less than double the ra- 

 dius of that in which she would turn when 

 steaming ahead. It is easy to see that if, to 

 avoid a collision, for instance, the screw be re- 

 versed, no reliance can be placed on the rudder, 

 llie ship may turn a little, and those in charge 

 may know in what direction she will turn, but 



the amount of turning must be small and the 

 direction very uncertain. It becomes a ques- 

 tion, then, whether danger may be better avoid- 

 ed by stopping, or by turning at full speed. 

 "When the helm is under sufficient command, it 

 is held to be the safest course to adopt the lat- 

 ter alternative ; and the reasons appear to be 

 conclusive. A screw steamship when at full 

 speed requires five lengths, more or less, in 

 which to stop herself ; whereas, by using her 

 rudder and steaming on full speed ahead, she 

 should be able to turn herself through a quad- 

 rant without having advanced five lengths in 

 her original direction. That is to say, a ship 

 can turn a circle of not greater radius than four 

 lengths, more or less; so that, if running at full 

 speed directly on to a straight coast, she should 

 be able to save herself by steaming on ahead 

 and using her rudder after she is too near to 

 save herself by stopping ; and any obliquity in 

 the direction of approach, or any limit to the 

 breadth of the object ahead, is to the advan- 

 tage of turning, but not at all to the advantage 

 of stopping. A method introduced at New 

 York, which consists in taking up the slack of 

 the tiller-rope; has proved very successful in 

 experiments. 



The Paper Manufacture. An instructive ex- 

 position was open at Berlin during the summer, 

 viz., an exhibition of paper. Besides writing 

 and printing papers and the other usual forms 

 of this useful material, there were exhibited 

 (all of paper) materials for house-building, fur- 

 niture, railway-wheels, boats, utensils of vari- 

 ous kinds, ornaments, etc. On the occasion of 

 this exposition statistics were published show- 

 ing the amount of paper consumed in different 

 countries. The United States use the largest 

 proportion, and Scandinavia the least. Italy's 

 consumption is small, and that of Russia much 

 smaller. The quantities used per capita in sev- 

 eral leading countries are stated as follows : 

 United States, 30'8 Ibs. ; Germany, 13'2 ; Eng- 

 land, 11; France, 7*92; Austro-Hungary, 5-5 ; 

 Russia, 1-98; Italy, 3'08; Scandinavia, 1-1; 

 Belgium, 11-22; Switzerland, 13-86. Further, 

 it is stated that 600,000,000 people use Chinese 

 paper and that 24,000,000 write on leaves, etc., 

 while 280,000,000 use neither paper nor any 

 substitute. The number of exhibitors at the 

 Exposition was about 500. A house of paper, 

 with furniture of the same material, was ex- 

 hibited ; also a sailing vessel of paper. 



A Substitute for #iZ/k. The attempt to util- 

 ize as a material for textile fabrics the lyssus 

 or silk-like thread with which Pinna nobilis, 

 a Mediterranean species of mussel, attaches 

 itself to objects, was made in antiquity with 

 some success, and has been repeated in mod- 

 ern times. The supply of the material being 

 precarious, the utilization of this material has 

 never led to any practical result. But now 

 a German naturalist, Tycho Talberg, proposes 

 to use the filaments or byssus of the common 

 edible mussel (Mytilus edulis) for the manu- 

 facture of a fabric resembling silk. This bys- 



