METEOROLOGY. 403 



Van Eysselberghe, exhibited by the Koyal Observatory of Brussels. 

 It gives its records not only at the place of observation but at one or 

 more distant stations, and gave every night at Paris a record of the 

 indications of the instruments at Brussels. Once every ten minutes it 

 comes into action, and registers one after the other the six following 

 elements: 1, temperature; 2, humidity; 3, water in rain-gauge ; 4, di- 

 rection of wind; 5, barometer; 6, velocity of wind. It also makes a 

 mark about every half-second, due to the action of clock-work at the 

 sending station. 



The registration is made by a diamond point on a thin plate of zinc, 

 which is bent round the surface of a revolving cylinder, which is 

 covered with lampblack to make the marks more visible. This plate 

 serves afterward for printing any number of copies. There may be 

 several of these cylinders at as many different stations, all receiving 

 simultaneously the indications furnished by any one station. By one 

 line wire and oue diamond point the curves for six instruments are 

 drawn at a station which may be 200 or 300 miles distant. The 

 value of such an instrument for furnishing the director of a central 

 station with accurate data on which to base his weather predictions 

 speaks for itself; and as regards expense, all the expenses of photog- 

 raphy and of reducing and engraving photographic traces are saved. 

 It has been worked in Belgium over a wire of the length of 750. miles. 

 [We do not, however, understand that such instruments can possibly 

 replace the services of a corps of intelligent observers ; certainly each 

 instrument would require an attendant mechanician.] {Nature, Octo- 

 ber, 1881, XXIV, p. 588.) 



M. Dufour describes an apparatus for indicating the variations of 

 chemical intensity of the sunlight. It has some likeness to Draper's 

 tithonometer ; its principle is opposing the variable action of light on 

 a mixture of chlorine and hydrogen, with an electric current (of varia- 

 ble intensity and measurable each instant), which by its i^assage causes 

 decomposition of a quantity of hydrochloric acid equal to that pro- 

 duced by action of light on the mixture of chlorine and hydrogen. The 

 apparatus is like a Rumford differential thermometer ; in one bulb is 

 some hydrochloric acid solution, with carbon electrodes; in the other 

 some sulphuric acid. The light acts on the former. One mode of meas- 

 urement is to note the time taken in displacement of the sulphuric acid 

 column a certain distance along the connecting tube. Then bring back 

 the column to its original position by passing the current. [Nature, No- 

 vember 25, 1880, XXIII, p. 87.) 



An instrument has been recently introduced by Messrs. Francis & 

 Co. (telegraph engineers, Hatton Garden, London) for the purpose of 

 receiving the " Greenwich time signal" at the various telegraph sta- 

 tions of offices and private firms who may be in communication with 

 the postal telegraph service. Hitherto the passage of the time-signal 

 current at 10 a. m. along the wires gave no indication of its pres- 



