FOR DETACHED OBSERVATORIES. 531 



movement of the two clocks, are formed by a number of points or 

 dashes made by the interruption of the current by little ebonite plates 

 in the divided arc of the apparatus at the detached ooservatoiy. It 

 the clock at that station has a faster or slower rate than that at the 

 principal station, these lines will not be parallel to the axis of the cylin- 

 der, but oblique, and in case of an irregular rate will even exhibit 

 sinuosities. We are thus kept informed of the state of things, and, if it 

 be impossible to go to the detached observatory, the main clock may be 

 made to keep time with the defective inaccessible clock, taking note, 

 of course, of the corrections which this alteration renders necessary. 

 The construction of a clock to run a year without winding is declared 

 by skillful clock-makers to present no difficulty, so that an observatory, 

 the essential details of which I have briefly sketched, may then operate 

 even on those steep peaks the ascension of which can only be made dur- 

 ing two summer months. A telegraph wire connecting the isolated post 

 with the main station is all that is necessary in order that the distant 

 observations be regularly registered. 



We have so far spoken of two independent clocks, but who that is 

 familiar with the improvements in telegraphs and electric clocks can- 

 not understand that the minute hand at the detached observatory may 

 be kept in motion by the same clock that turns the cylinder at the prin- 

 cipal station? For this purpose, however, a second telegraphic wire 

 would be necessary, which would uselessly increase the expense of es- 

 tablishing the outlying station. 



But, adopting another arrangement, I believe that the same wire may 

 serve both to move the hand — which we will still call the minute hand, 

 though it does not now deserve the name — and to transmit the indica- 

 tions of the instruments. We have before considered that the minute 

 hand will make one revolution in an hour, so that, according to the 

 state of the instruments, the record of the barometer is made, for example, 

 at ten minutes past twelve, that of the thermometer at twenty-eight 

 minutes past twelve, the hygrometer a quarter of an hour later, and 

 those of the direction and velocity of the wind and the rain-fall in the 

 fourth quarter of the hour. But such a difference would not satisfy 

 meteorologists who prefer the simultaneous observation of all the instru- 

 ments so as to have a complete view of the state of the atmosphere at 

 any given moment. Consequently, instead of having the minute hand 

 at the detached observatory and the cylinder at the central station make 

 one revolution during the space of an hour, I propose to have them make 

 the entire revolution in a very short space of time — a few minutes at 

 most— the hand and the cylinder remaining at rest during the remainder 

 of the hour. Once an hour the clock of the principal station would raise 

 a catch at the other station, and the apparatus would then be set in 

 motion by means of a weight or spring so regulated by a, pendulum as 

 to make a complete revolution in two or three minutes — the cylinder at 

 at the main station being put at the same time into isochronous motion. 



