Page:Transactions NZ Institute Volume 30.djvu/74

 Ngatiawa [who were returning by sea] reach that place give them the money the bank-manager will pay you." I travelled day and night overland, and overtook the steamer at Tauranga, and I got the bag of money from the bank, and took it to the people, saying, "Behold! I have brought you a koha (gift) from your grandparent, Hotereni Taipari." £1,000 in single bank notes did I give them, and Ngatiawa went on their way rejoicing. 

VI.—The Insulation of Cold-stores.

By Professor F. D..

a low temperature is artificially maintained in any space, such as a portion of the hold of a steamer, a room in a freezing-works or butter-factory, or in a railway-truck, it is necessary to prevent, as far as possible, the access of heat from the outside. This is done by providing an internal lining to the walls and roof, distant from them some 12 in. to 18 in., and packing the intervening space with some material which does not readily allow heat to pass through it. Charcoal has hitherto been generally employed for this purpose, but it is claimed that pumice-stone is more suitable; while it is conceivable that other substances known to be good insulators might be employed with advantage.

It seemed desirable to institute an exact comparison of the insulating powers of these substances, and the following is a description of some experiments made with this object in view:—

The apparatus employed is shown in Plate XI.; it consisted of a small cylinder A of thin brass, 2 in. in diameter and 7 in. high, surrounded by a double cylinder or jacket BB made of copper. The internal diameter of this second cylinder was 5$3⁄8$ in. and its height 10$5⁄8$ in.; so that A, when placed centrally, was separated from BB by a space 1$11⁄16$ in. wide. This space CC was loosely packed with the charcoal or other substance to be experimented upon. The cylinder A was provided with a thermometer T, divided into tenths of a degree centigrade, and of such an open scale that hundredths of a degree could be easily distinguished by means of a suitable reading-telescope, which instrument was employed through-