December 18, 1885.] 



SCIENCE. 



547 



simply, ' Do you get me now?' After some fur- 

 ther interchange of compliments, the operator on 

 Naushon was directed to seal up the end of the 

 cable by covering the exposed wire with gutta- 

 percha. This having been done, communication 

 ceased, and the insulation was tested. A number 

 of battery cells were joined ' in series ' to the 

 galvanometer, which was a delicate instrument of 

 high resistance, with a reflecting mirror, and to 

 this the end of the cable was attached. The test 

 was practically an endeavor to force the current 

 through the gutta-percha insulation, the amount 

 of the leak being measured by the deflection of 

 the galvanometer needle. It had been demanded 

 of the cable that it should show an insulation 

 resistance of at least two hundred and fifty meg- 

 ohms per mile, and it greatly exceeded this number 

 when tested. 



A few days later, when wind and weather were 

 favorable, the island of Nantucket was connected 

 in a similar way with Martha's Vineyard, the 

 cable taking a sweep out into the sea to avoid 

 shoals ; and finally a short piece, about a mile in 

 length, was made to connect Naushon, by way of 

 the little island Uncatena (always ' Uncle Timmy ' 

 at home), with Wood's Holl, and thus was com- 

 pleted the union of these islands with the main- 

 land, which it is hoped may last for many years. 



M. 



PHYSICS AT JOHNS HOPKINS. 



The large and weU-appointed laboratories re- 

 cently erected by the trustees of the Johns Hopkins 

 university for the chemical and biological depart- 

 ments have by contrast made the more evident 

 the needs of the physical department, which has 

 been obliged to occupy temporarily parts of four 

 different buildings. The trustees, recognizing this 

 need, are now erecting a buildiag for a physical 

 laboratory. The new laboratory is to be a hand- 

 some building of red brick, trimmed with brown 

 sandstone, and wiQ occupy a fine site about a block 

 from the other university buildings, on the corner 

 of a quiet little street midway between the more 

 important streets, which carry the bulk of the 

 traffic of that region. It will therefore be as free 

 from disturbance from the earth vibrations as 

 could be expected in a city. 



The building wfil be 115 feet long by 70 feet 

 broad, and wiU have four stories besides the base- 

 ment. In the centre of the building, and below 

 the basement, are several vaults for iustruments 

 requiring to be used at constant temperature, also 

 a fii'e-proof vault for storage. In these vaults will 

 be jjlaced Professor Rowland's dividing-engine, 

 by which the diffraction gratings are ruled, and 



the Rogers-Bond comparator, which has recently 

 become the property of the university. In the 

 basement will be rooms for the mechanical work- 

 shop, for furnaces, and for piers for instruments 

 requiring great stability. The first floor will in- 

 clude the main lecture-room, which will accom- 

 modate 150 persons, and rooms for investigations 

 by advanced students in heat and electricity. The 

 second floor will contain mathematical lecture- 

 rooms, studies for instructors, and a room for the 

 mathematical and physical hbrary of the univer- 

 sity. 



The elementary laboratory will be on the third 

 floor, which will also have rooms for more ad- 

 vanced work. The fourth floor will contain rooms 

 for special work in light. 



There will be a tower on the south-east comer 

 of the building, which will have two rooms above 

 the fourth floor. The upper of these wfll be pro- 

 vided with telescope and dome, and wiU be a con- 

 venient observatory when great steadiness in the 

 instruments is not required. There wfll be power 

 in the building for driving the machinery in the 

 workshop and for running the dynamo-machines. 

 A large section of the building is to be made en- 

 tirely free from iron. The sash- weights will be of 

 lead, and the gas-pipes of brass. Brackets wfil be 

 attached to the walls, on which galvanometers 

 and cathetometers may be placed. In order to 

 avoid the inconvenience of having piers go up 

 through the lower rooms, and yet to secure steadi- 

 ness, beams have been introduced into the floors, 

 which reach from one wall to the other between 

 the regular floor-beams, and do not touch the floor 

 at any point. If, now, a table is made to rest on 

 two of these beams, by making holes in the floor 

 over them to admit the legs of the table, it is 

 entirely undisturbed by any one walking over 

 the floor, except by such motion as is transmitted 

 to the walls. There will also be a small vertical 

 shaft in the wall of the tower, running from top 

 to bottom, in which a merciu'ial manometer may 

 be set up. 



The vaults for constant temperatiu*e have been 

 built with double walls, so that a current of air 

 may be drawn between them whenever deshable 

 to prevent dampness. It is expected that the 

 laboratory will be ready by October next. 



The photographic map of the spectrum, upon 

 which Professor Rowland has expended so much 

 hard work during the past three years, is nearly 

 ready for publication. The map is issued m a 

 series of seven plates, covering the region from 

 wave-length 3100 to 5790. Each plate is thi-eefeet 

 long and one foot wide, and contains two sti'ips 

 of the spectrum, except plate No. 2, which con- 

 tains three. Most of the plates are on a scale thi-ee 



