ENGINEERING. 



EPIDEMICS. 



311 



them underground. According to the report 

 of Dr. Scluiyler S. Wheeler, of the New York 

 Board of Electrical Control, New York has 

 4,453 miles of underground wires ; Paris, 4,100 ; 

 Brooklyn, 2,100 ; Chicago, 200; Boston, 400; 

 and Pittsburg, 1,000. These figures probably 

 considerably understate the mileage in opera- 

 tion at the end of 1888, but they are the latest 

 available for the foreign cities. New York 

 city has been to a more serious extent the vic- 

 tim of overhead wires than any other large 

 city, and all sorts of devices, legal and other- 

 wise, were resorted to in order that no change 

 should be made. After long delays, laws 

 were passed sufficiently 

 stringent to compel the 

 laying of subways, and the 

 capacity of subway con- 

 struction now finished is 

 given by the report as 

 about 34,665 miles. 



About 600 patents and 

 plans relating to under- 

 ground systems for wires 

 were examined before a 

 final decision was reached. 

 It appeared that no sys- 

 tem as yet devised could 

 be regarded as wholly sat- 

 isfactory, the nature of 

 electricity being such that 

 where wires are bunched 

 or even near one another 



they 

 suffer 



mutually '""<%m 

 from what \ ^ 

 is known to ' 

 electricians as 

 "induction," the 

 result being a loss 

 of efficien 



The system finally 

 adopted is shown in 

 the illustrations. Fig. 12 shows a conduit with 

 its pipes partially covered in. On top of the 

 main conduit is shown a section of the Edison 

 incandescent illuminating system. Fig. 13 

 shows the interior of a manhole, and Fig. 14 the 

 lamp-post adopted by the board with the store 

 and house connections. The pipes are of iron 

 four inches in diameter and in lengths of twen- 

 ty feet. They are laid in hydraulic concrete 

 to secure insulation, and the wires separately 

 insulated are passed through them by means 

 of a jointed rod, such as is used by chimney- 

 sweepers, and may be taken out for examina- 

 tion or repair. 



Railway Tnnnels in Russia. It is worthy of re- 

 mark that, notwithstanding the very great ex- 

 tent of the Russian Empire, but few tunnels 

 have had to be excavated for its railroads. 

 Till recently tunnels have been used only in the 

 Polish provinces and the Ural ; now the tun- 



FIG. 14. LAMP-POST 

 DISTRIBUTION. 



nels of the Caucasus may be added to the list. 

 The Novorossisk branch of the Caucasus Rail- 

 road passes through two tunnels, the longer of 

 which is 1,338 metres, and the shorter 365 

 metres in length. The Souram Tunnel of the 

 Baku-Batoum Railway, which was opened on 

 the 31st of October, is the largest tunnel in 

 Russia, being 4'4 kilometres, or a mile and 

 three quarters long. By its means the steep 

 grades of the Souram Pass are avoided, and 

 the petroleum trains, which formerly had to be 

 divided at this point, are now able to pass to 

 the Black Sea unbroken. 



EPIDEMICS. At certain periods in the his- 

 tory of mankind certain diseases have attained 

 such force as to affect large areas of territory 

 and kill great numbers of men; and have then 

 been known as epidemics. It is the design of 

 this article to sketch the general history of the 

 greatest of these epidemics. 



The Black-Death. One of the most memor- 

 able of the epidemics of the middle ages was a 

 great pestilence in the fourteenth century, 

 which devastated Asia, Europe, and Africa. 

 It was an Oriental plague, marked by inflam- 

 matory boils and tamors of the glands, such as 

 break out in no other febrile disease. On ac- 

 count of these boils and from the black spots 

 (indicative of putrid decomposition) which 

 appeared upon the skin, it has been generally 

 called the black-death. The symptoms were 

 many, though not all were found in every 

 case. Tumors and abscesses were found on 

 the arms and thighs of those affected, and 

 smaller boils on all parts of the body ; black 

 spots broke out on all parts of the skin, either 

 single, united, or confluent. Symptoms of 

 cephalic affection were frequent ; many pa- 

 tients became stupefied, and fell into a deep 

 sleep, losing also their speech from palsy of 

 the tongue; others remained sleepless, without 

 rest. The fauces and tongue were black, and 

 as if suffused with blood. No beverage would 

 assuage the burning thirst. Contagion was 

 evident, for attendants caught the disease from 

 their relatives and friends. But still deeper 

 sufferings were connected with this pestilence : 

 the organs of respiration were seized with a 

 putrid inflammation, blood was expectorated, 

 and the breath diffused a pestiferous odor. 

 The plague spread with the greater fury, as it 

 communicated from the sick to the healthy: 

 contact with the clothes or other articles 

 which had been used 1 by the infected induced 

 the disease, and even the breath of the sick, 

 who expectorated blood, caused a contagion 

 far and near. As it advanced, not only men, 

 but animals also fell sick and expired. 



In England the plague first broke out in the 

 county of Dorset, whence it advanced through 

 the counties of Devon and Somerset to Bristol, 

 and thence reached Gloucester, Oxford, and 

 London. Probably few places escaped, per- 

 haps not any, for the annals of contemporaries 

 report that 'throughout the land only a tenth 

 part of the inhabitants remained alive. From 



