320 PETTEnSSON ON WATER AND I C E. 



it receives and gives out heat to the at- 

 mosphere, the surrounding water, etc. . . by ra- 



diation and convection, q-2, qs, ^,i^... 



it separates from the surrounding water 



at — 2° C [abs. temp. T' = 271] by freezing as 



ice + solid cryohydrates, ^ thereby developing 



■p 

 the latent heat R ^, r 



the ice receives and imparts heat to the 



atmosphere etc. . . ri, r-2, . . .• iL, £l . . . 



3. The algebraic sum of the fractions: 



Q, ii ... ^, Il ... etc... =0, 



T ' Ti T' 'Ti' 



since the ice is supposed to return to its initial state. We 

 •can not evaluate all these quantities, but we nevertheless can 

 form an idea of the character of the whole cycle from the 

 head members 



^ and ^5 



the influence of which must be predominating. If we leave 



aside the secondary changes, represented b}^ ^ , j^...f^., ^ 



etc. . . we conclude from the fact, that 



Q > Pv and T > T', 



that the result of the melting and freezing of sea-ice is two- 

 fold, viz: 



a quantity of heat, R, is transported as thermic energy 

 from one part of the ocean (where the melting takes place) to 

 another (where the water freezes again); 



another quantity of heat can simultaneously be trans- 

 formed into mechanic energ^^ If we assume T = — 0°. . . C 

 and T' = — 1°.9, the quantity of heat availahle for mechanic 

 effect would be 



Q ^Lzi^ = 0.55. . Cal. for eyery kgr. of ice. 



We must expect it to be far less in reality. That part of the 

 availahle energy, which is really transformed into work, is 

 surely too small to influence the experimental measurements. 

 Exact calculus is impossible at present, because we do not 

 know the exact value of the quantities T, R, qi, q-i • . . etc. . . 



' Some unfrozen cryohydrates will also be enclosed in the new sea-ice, 

 which afterwards sohdify and nielt as the temperature falls or rises. The 

 thermic influence of these processes will on the whole neutralize each other. 



