142 THE NATIONAL SCIENTIFIC INSTITUTIONS AT BERLIN. 



The cable examination-room serves iu the first line for continued 

 measurements of the underground lines of Berlin, which are made once 

 a week ; it is furthermore used for the accurate measurements and ex 

 periments with new batteries, apparatus, and switches, etc. The cur- 

 rents of the two underground cables, Berlin and Thorn and Berlin and 

 Dresden, are measured by the aid of two self- registering apparatus lo- 

 cated in the testing-room. 



The use of underground cables made it desirable to test their elec- 

 trical properties at regular, short intervals by measuring the resistance 

 of the copper wire, the isolating resistance, etc., of the insulating mate- 

 rial, etc. This had the effect of giving full information of the state of 

 the cable at all times ; any mechanical injury was at once indicated, and 

 could be repaired without delay. These regular measurements offered 

 an opportunity for the instruction to a large number of officials located 

 throughout the Empire, thus enabling them to be of service iu case of 

 emergency. 



The Postal Museum. — The collections of the postal museum are located 

 on the ground floor of the monumental building of the central Post- 

 Office Department of the German Empire. 



The Postmaster General, soon after entering upon his duties, endeav- 

 ored to interest the official bureaus, private individuals, artists, scien- 

 tists, etc., in his ideas, and succeeded therein in such a measure that at 

 the beginning of the present decade already a pretty complete repre- 

 sentation from the beginning of communication to the present days, was 

 presented in the collections of the postal museum. 



In the mean time, by the incorporation, in 1876, of the telegraphy 

 with the post, all the apparatus, models, materials, etc., collected by 

 the former general director of telegraphy were transferred to the older 

 sister establishment, and this collection being very rich and complete, 

 the telegraph division of the postal bureau offers to the technician and 

 to the physical science a rich source for earnest study, and especially 

 a true historical picture of the development of the telegraph. 



The postal division, of course, is still more extended, for the history 

 of communication is as old as man himself. In the museums are rep- 

 resented the Egyptians, Assyrians, Persians, Hebrews, and other people 

 of antiquity : Egyptian hieroglyphs, papyrus with hieratic writing, and 

 Niniveh writing upon terracotta plates are the proofs which those 

 people offer. The little plates of the Greeks and Romans which were 

 laid before the oracle of Dodous, the skytale written upon parchment, 

 the well executed imitations of the rare ^'•tabellcv duplices et trip- 

 lices^^ and the '' Diptyches,^^ distributed by the Koman consuls upon the 

 commencement of their terms of office, conclude the antiquity. The 

 gradual development of more regulated forms of later periods, includ- 

 ing the Middle Ages, are illustrated by precious samples of writings 

 emanating from the contemplative quiet of the monasteries, representa- 

 tions of boats, wagons and teams, streets, ships, etc., etc., while the 



