1879.] 



Presents. 



297 



and ( C"~ -C' 2 ) = (T" - T - T' + T) - = (T" -T')|, 



R R 



but for small differences of C" and C we may put 

 (C" 2 -C' 2 )=2C"(C"-C') 3 



that is to say, small variations of current will be proportional to the 

 variation in the temperature of the strip. 



In order to facilitate the process of determining the value of a 

 diagram in webers or other units of current, it is only necessary, if 

 the variations are not excessive, to average the ordinates, and to 

 determine their value by equation (1), or from a table prepared for 

 that purpose. The error committed in taking the average ordinate 

 instead of the absolute ordinates, when the current varies between 

 small limits, is evidently small, the variation of the ordinates above 

 their mean value averaging the variations below the same. 



The thin sensitive conductor may thus be utilized either to restrict 

 the amount of electricity flowing through a branch circuit within 

 certain narrow limits, or to produce a record of the amount of current 

 passed through a circuit in any given time. 



Presents, January 9, 1879. 



Transactions. 



Dresden: — Verein fur Erdkunde. XV Jahresbericht. Wissen- 



schaftlicher Theil ; Geschaftlicher Theil und Sitzungsberichte. 



8vo. 1878. The Society. 



Haarlem : — Hollandsche Maatschappij der Wissenschaffcen. Natuur- 



kundige Verhandeliugen. Derde Verzameling. Deel 3. 4to. 



1878. Archives Neerlandaises des Sciences Exactes et Natu- 



relles. Tome XIII. liv. 1-5. 8vo. 1878. The Society. 



Musee Teyler. Archives. Vol. IV. fasc. 2-4. Vol. V. Partie 1. 



8vo. 1878. The Musee. 



Helsingfors : — Societas pro Fauna et Flora Fennica. Acta. Vol. I. 



8vo. 1875-77. Meddelanden. Haftet 2-4. 8vo. 1878. 



The Society. 



Innsbruck : — Ferdinandeum fur Tirol und Vorarlberg. Zeitschrift. 



Dritte Folge. Heft 22. 8vo. 1878. The Institution. 



London : — British Pharmaceutical Conference. Transactions at the 



Fifteenth Annual Meeting, held in Dublin, August, 1878. 



Year Book of Pharmacy, 1878. 8vo. The Conference. 



St. Bartholomew's Hospital. Reports, edited by W. S. Church 



and Alfred Willett. Vol. XIV. 8vo. 1878. The Hospital. 



VOL. XXVIII. Y 



