1877.] On the Growth and Variability of Madreporaria. 133 



taneously with the dynamical expansion and masks its true amount. This 

 is divisible into high and low temperature contraction. [Compare figs. 

 4 & 5.] 



2. The presence of a cooling expansion or crystallization, which 

 comes in during the dynamical contraction and masks its true amount. 



3. These effects, due to crystallization and decrystallization, are the 

 causes of the so-called kicks, or temporary contractions and expansions, 

 which occur during the heating and cooling of the steel. 



4. That the low-temperature contraction and cooling expansion are due 

 to decrystallization and crystallization which occur during the acts of 

 heating and cooling, while the kicks themselves are simply the thermal 

 effects associated with these changes, and are proportionate to their 

 extent. 



5. That protracted annealing (that is, extremely slow cooling) brings 

 about molecular separation of the carbon and iron ; and steel in such a 

 state contracts greatly when high temperatures are reached, producing 

 the contraction returns seen at the end of the heating, and which are due 

 to the condensation produced by the recombination of the carbon and 

 iron. Steels in this state are less susceptible to cooling-expansion 

 (crystallization), and therefore to low-temperature contraction on sub- 

 sequent heating. [ Vide fig. 5.] 



EXPLANATION OF THE WOODCUT. 



Fig. 1. Commercial steel wire. First heating. 

 Fig. 2. Do. do. Second heating. 



Fig. 3. Air-hardened wire. 

 Fig. 4. Water-hardened wire. 



Fig. 5. Annealed steel wire. High-temperature contraction. Contraction returns. 



N.B. — In each figure the upper curve refers to the heating-, the lower to the 

 cooling-effect. 



II. " On the Rapidity of Growth and Variability of some Madre- 

 poraria on an Atlantic Cable, with remarks upon the rate of 

 accumulation of Foraminiferal Deposits/' By Prof. P. Martin 

 Duncan, F.R.S., Pres. Geol. Soc. Received March 15, 1877. 



A telegraph-cable was laid off the north-west of Spain in 1870, and a 

 portion of it was recovered in 1876, in long. 9° 4' W. and lat. 44° 6' N. 

 The depth from which the recovered portion came was from 522 to 550 

 fathoms ; the ground was conglomeratic, and there was a deposit there 

 of sticky foraminiferal mud. Much coral growth had occurred on the 

 cable, and when it was fished up some living and dead f orms, together with 

 Echini, Pectens, and mud, came up from off the surrounding sea-floor. 



The growth on the cable consisted of numerous individuals of Lesmo- 



