l; 



644 



REPORT — 1884. 





ii 'iu 



IG. On the Formation of Frasil Ice. Bij G. II. Hensqaw. 



The author suggests tlie theory that ' frasil ice ' is a true growth upon substancps 

 l)ane;ith the surface of the water, due to the refrigeration of tliese nuck'i by cold 

 currents, in contradistinction to the tlieory that this ice is first formed on the 

 surface, and afterwards carried down by currents and attached by a process of 

 regelation to substances at the bottom. 



17. Kote on the Internal Temperature of the Earth at Westcille, 

 Nova Scotia. By H. S, PoOLE, F.G.S. 



On the shvpe or incline of tlie Acadia colliery in tiie Picton coalfield, reaching 

 a length of 2,-V)0 feet, at a depth of 000 feet below the outlet, holes were bored in 

 the freshly mined coal, thermometers inserted, the openings closed, and the 

 temperature taken after some hours. The experiment was lepeated, and the record 

 of 55" Fahr. verified. 



The ground immedicately over the experimental station falls away with the dij) 

 of the measures, and is at that point about 030 feet in thickness: taking tiiis as 

 the depth, and allowing for the depth at which tlie mean surface temperature 

 (42' Fnhr.) is uniform by adding 1 to 13 (the dillerence in degrees between tlie 

 surface mean temperature and that observed in the coal !it the bottom of the incline), 

 the number 14 is divided into 030, the depth, and the result obtained is an average 

 depths of GO feet for each degree in temperature. 



The practical interest attached to such an experiment lies in connection witli 

 the depth at which in the future coal may be mined in Nova Scotia without 

 inconvenience from high temperature. 



The initial mean temperature being 0" (?) below that oftheNortli ofEngland,is, 

 according to this experiment, equal to a deptli of GOO feet greater than in England 

 before a corresponding temperature is reached. 



So far as is at present known, it is probable that seams of workable thickness 

 in tlie I'icton field lie at a depth of 4,000 feet; in the ('iimberland Held at still 

 greater depth; and in Cape Breton, where the seams dip under the ocean, there is 

 every reason to believe they extend to great distances and depths. 



In the anther's report as Inspector of Mines, in 1877, he referred to the value 

 of these submarine fields, and to the necessity for care in working in our own day 

 the out-crops of the seams near the shore, in order that the wealth seaward may liu 

 secured for our successors. 



18. On the Formation of Mackerel Ski/. Bij Dr. H. Mcirhead. 



At the Glasgow meeting of the Association in 1870, Sir AVilliam Thomson read 

 a short note on the formation of mackerel sky. The author having paid niHcli 

 attention to the various aspects of the congeries of cloudlets so named, has come 

 to the conclusion that the following is the usual mode in which they are generated. 

 (iiven a tliinnisli stratum of air moist in process of passing over a drier and cooler 

 body of air, of dillerent velocity or direction. The vapour by cooling will become 

 visible, and from friction the stratum will get rolled into long cylinders. Now let 

 another current of air brush across the cylinders at right angles to their length, or 

 indeed any large angle. This will have the effect of rolling the thinnisli stratum 

 into cylinders crossing the first .set. And now neither set will appear as long con- 

 tinuous rollers, but from being crossed will show as a congeries of little cloudlets 

 or drums, i.e.. mackerel sky. 



In favour of this hypothesis it may be noted that if attention be paid to the 

 cloudlets there will often be observed, at one or other e.'ctremity of the formation, 

 portions of the cylinders which extend continuously for a considerable length 

 where they have not been divided into drums by a crossing current. Again, if one 

 of the currents moves too rapidly, some of the cloudlets will get so torn by it that 

 they will often show as wisps or mare's tails. Moreover, it may sometimes lie 

 observed that when a long slender cloud is sailing end-long across the sky, that ii 



m 



