INDEX. Tol 
P 
Periodicals, and other Works procured by Purchase or Exchange 727. 
Photographs of Electric Sparks in Hot and Cold Avr, 425. 
Placentation of Seals, 275. 
Placentation of the Sloths, 71. 
Prarr (Dr Gustav). On the Establishment of the Elementary Principles of Quaternions on an Ana- 
lytical Basis, 175. 
On the Elimination of a, B, y, from the conditions of Integrability of Swadp, SuBdp, 
Suydp, 251. 
Q 
Quaternions, Establishment of the Plementary Principles of, on an Analytical Basis, 175. 
R 
Rhombohedral Carbonates of Scotland, 493. 
Seals, Placentation of the, 275. 
Sloths, Placentation of the, 71. 
Stark (Dr Jamas). On the Shedding of Branches and Leaves in Conifer, 651. 
Statutory Meetings, 671. 
Stresses Due to Compound Strains, 473. 
ar: 
Tart (Professor G.). On Orthogonal Isothermal Surfaces, 105. 
—— First Approximation for Thermo-Electric Diagrams, 125. 
Photographs of Electric Sparks in Hot and Cold Air, 425. 
TatBot (Henry Fox). Essay toward a General Solution of Numerical Equations of all Degrees, having 
Integer Roots, 303. 
Thermo-Electric Diagram, First Approximation to a, 125. 
Torule and Bacteria, Contribution to the Natural History of, 313. 
Traquair (Dr Ramsay H.). On the Structure and Affinities of Tristichopterus alatus (Egerton), 383. 
Tristichopterus alatus, Structure and Affinities of, 383, 

Tropeolum peregrinum (L.). Embryology of, 223. 
Tropceolum speciosum (Endl. and Poepp.), Embryogeny of, 223. 
Turner (Professor Wiiu1am). On the Placentation of the Sloths, 71. 
On the Placentation of the Seals, 275. 
On the Placentation of the Sloths, 71. 
Tweed, Drift Deposits in the Valley of, 513. 
High Water Marks on the Banks of the River, 513. 
U 
Upheuval of Scotland in its Central Parts, 39. 
END OF VOLUME TWENTY-SEVENTH. 
