Jdne, 1902.] 



KNOWLEDGE. 



123 



The smallness oi the objectionable luotloii is, indood, 

 one of the most remarkable results of the Coniiiiittee's 

 work. In the solid stone or floors in the basements and 

 iu the walls themselves, it was rarely found to exceed one 

 t)r two ten-thousandths of an inch, and such vibrations, 

 even if they recurred at the rate of fifteen jier si'cond. 

 would in all probability escape notice. On the hii^rher 

 floors, however, the vibrations have an amplitude which 

 may amount to, though it seldom exceeds, a thousandth 

 of an inch, but it is these vibrations, when their frequency 

 is over ten per second, that have given rise to such wide- 

 sjtreail annoyance. 



From the last curve, il, in Fig. -t, it is clear why the 

 vibration should be so much more marked on a floor than 

 in the basemerit. We see that, after a single stamp, the 

 floor makes quite a large number of oscillations before 

 it comes to rest again ; also, if we compare the curves 

 (I and (7 ui tlie same figure, that the period of the floor's 

 oscillations is very nearly the same as that of the jirincipal 

 vibrations caused by passing trains. Thus, vibrations, 

 which iu the basement are almost imperceptible, produce 

 increased vibrations in the floors, just as one particular 

 string of a jiiano resounds if the corresponding note be 

 struck outside. How greatly the original vibrations may 

 be magnified depends on the closeness between their period 

 and that of the floor's oscillations, and on the slowness 

 with which the latter die awa}'. If the two periods happen 

 to be nearly equal we may, therefore, expect a well-made 

 floor to have larger vibi-atious set up by resonance than 

 one in which the boards are unsound and the joists 

 badly laid. 



In the opening inquiry, nearly all the witnesses 

 e.vamined by the Committee stated that at times unusually 

 severe vibrations were felt. As these might be caused by 

 particular trains, simultaneous observations were made 

 during one day iu three houses from which rom]ilaints had 

 been received. The observers were placed iu different 

 rooms and noted the times at which the vibrations were 

 felt, and also estimated roughly their intensity, whether 

 severe, moderate or slight. Others in the two adjoining 



" MAAA An/Xr 



stations noted the times of arrival and departure of the 

 trail's, which were about 300 in number. The analysis 

 of the observations showed : " (a) That it was a matter of 

 chance whether a given locomotive caused a slight or a 

 severe vibration ; (6) That trains causing severe vibra- 

 tions in <me hoiise were as likely as not to cause only 

 slight vibrations in the others ; (c) That different rooms 

 in the same house were not similarly affected by the same 

 train." Owing to the waviness of the rails and wheels, 

 and to the random manner in which the irregularities of 



the wheels meet those of the rails, it is evident that there 

 may be times when several jiairs of wheels may be in a 

 position to cause strong vibrations simultaneously. 



When the work of the Committee began, the locomotives 

 in use weighed forty-four tons, and the unspriug- borne load 

 on each of the foiu' axles was eight tons. Two new types 

 were constructed shortly afterwards, and were tested by 

 the same methods. In the geared locomotive the total 

 weight is thirty-three tons, and the unspring-borne load is 

 reduced to two-and-a-half tons per axle; in the multiple 

 unit train, the weight of the motor carriage is twenty 

 tons, ami the unspring-borne load is still further reduced 

 to oue-and-three-quarter tons per axle. 



The effects of the different types of trains are well 

 shown in curves a, b, c, of Fig. 4, which correspond to the 

 ordinary locomotive, the geared locomotive, and the mul- 

 tiple unit train respectively. The vibrations produced by 

 the traius are, in fact, roughly pro]iortioual to the unspring- 

 borne load, for those due to the ordinary locomotive are 

 more than three times as great as those of the geared 

 locomotive, aud more than five times as great as those 

 produced by the multiiilc unit train. 



The observations made on the dift'erent trains also prove 

 that the locomotives are almost entirely responsible for 

 the disturbances, for the passenger coaches were prac- 

 tically identical in all the trains, and the only vibrations 

 that could, as a rule, be registered when the multiple uuit 

 train passed were those made by the motors at either end. 



The chief practical results of the enquiry may therefore 

 be summed up as follows : — (1) One method of lessening 

 the annoyance would be to reduce the irregularities of the 

 rail-surfaces ; aud, if a very high speed (say, of a hundred 

 miles or more an hour) were ever employed, this improve- 

 ment might become necessary. (2) But with the speeds 

 at present customary, by far the simpler and more 

 efficacious method is to reduce the unspring-borne load in 

 the locomotives to less than two tons per axle. 



ACROSS RUSSIAN LAPLAND IN SEARCH OF 

 BIRDS. 



By Harry F. Witherby, f.z.s., m.b.o.u. 

 III.— FOREST, LAKE AND MARSH. 



OuE first camping place in Russian Lapland was 

 charmingly situated on the shores of a little lake the 

 surface of which sparkled brightly in the sun, while 

 behind us the river shone white and foaming every here 

 and there between the birch and pine trees. There were 

 a good many birds about. The golden-eyed duck,* the 

 most n^^merous duck iu this country, aud very good eatiug, 

 was plentiful but not easy to get. One which we shot 

 fell in the water, and being caught by the stream flowing 

 through the lake was hurled down the river at a furious 

 pace. One of our men ran after it, but returned perspiring 

 in half-an-hour or so, saying that it must by now have 

 reached Kandalax. The pretty three-toed woodpecker,t 

 which is much like our spotted woodpecker, but has only 

 three toes, and a yellow head, was common, aud although 

 apparently not nesting was often to be found in a hole iu 

 a tree. Like our woodpeckers, these birds no doubt roost 

 in holes of trees, and as we found them in these hiding 

 places at all times of the day and night, we came to the 

 conclusion that iu these regions birds, like men, take their 

 sleep just when they feel they need it. Other birds were 

 about all night— the familiar cuckoo J was often to be 



* Clangtda glaucion. + Ficoides tridactylus. 



1 Cuculiis canorui. 



