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Show 1870.] INTRODUCTION OF SALMON INTO TASMANIA. 19 hatched safely after being buried in ice 150 days, has been fully pnblished to the world ; but why this was likely to prove successful has not perhaps been publicly explained. Even Mr. Frank Buck-land, in his book on fish-hatching, speaks of freezing the ova, and thereby greatly misleads his readers. It was long ago shown that actually to freeze ova was to kill them in a few days, or, at most, weeks. The question then was, how could they be kept at an equable temperature just above the freezing-point 1 If a block of ice (the sensible temperature of which is 32° Fahrenheit) be immersed in water of a higher temperature, a portion of the ice will melt until the heat of the water falls to 32° F., but no more of the ice will be afterwards melted until the temperature of the water is again raised. If the ice could cool the water below 32°, a portion of the water would be frozen ; but to effect this, a further portion of the ice must be melted, and water at 32° is not capable of melting ice. If vessels containing creams be immersed in ice for a month, no change takes place in their contents ; but convert a portion of the surrounding ice to water by the admixture of any deliquescent salt, and the submerged creams are instantly frozen. Therefore by this beautiful provision of nature any substance above the freezing-point buried in ice can never fall to the freezing-point till the ice next to it is converted to water ; and so long as any ice remains, the buried substance will continue at a low temperature certainly, but above the freezing-point; and to this principle success was due. After many interviews with the owners of various ships, Mr. Youl (to whom Tasmania is greatly indebted for his determined perseverance in this respect) received the munificent offer from Messrs. Money, Wigram, and Co. of 50 tons of room gratis in their clipper-ship ' Norfolk,' bound to Melbourne. An ice-house capable of holding 30 tons was built in a situation admirably chosen for the purpose-on the lowest deck, amidships, and equidistant from stem and stern, in the position in which the motion of the vessel would be least felt. With much difficulty, and at the cost of great personal exertion on the part of all concerned, ahout 90,000 ova of the Salmon (Salmo salar) and about 1500 ova of the Trout (Salmo fario) were obtained and safely packed in deal boxes, each a foot long, 8 inches wide, and 4 inches deep. In some of the boxes a layer of charcoal was first placed on the bottom, then a layer of moss damped in pure water ; then ova were lightly placed on the moss, and the whole covered with another layer of damp moss, upon which the lid was screwed down. In the remaining boxes the charcoal was omitted, the packing otherwise being the same. Through the lid and bottom of each box several small holes were drilled; and all the ova were packed in 181 boxes. The boxes were next placed on the bottom of the ice-house, which was filled up with Wenham-Lake ice, and the whole securely closed. All being complete, the vessel sailed from London towards the end of January 1864, and left Falmouth on the 28th of that month. On the 15th of April the 'Norfolk' arrived in Melbourne. On the next day the ice-house was opened and the small boxes unpacked. The lid of one box was then re- |
