122 Transactions. — Miscellaneous. 



learned from the manuscript in the Sloane collection of the 

 British Museum. It is but within the last few years, com- 

 paratively speaking, that chronometers have been in universal 

 use. 



The last antiquated marine instrument to which I shall 

 refer as used in Tasman's tnne is the sand-glass. These 

 were constructed of different sizes, so as to measure periods 

 of four hours, one hour, and half an hour The survival 

 of them at sea is to be seen in the 28-second log-glass, 

 used when the log is taken ; and on the kitchen mantelpiece, 

 for boiling eggs. Hour-glasses were used in the last century 

 in churches, placed on the pulpit-ledge in view of the con- 

 gregation, where they regulated the length of the sermon. 

 Much improvement has been effected in this direction during 

 the last few years, the regulation length of sermons now being 

 about twenty minutes. The time at sea was roughly kept by 

 the half-hour glass, which was always in sight of the steers- 

 man. When the last grains of sand had run out he reversed 

 the glass, striking a bell at the same time as a mark of the 

 time. This was repeated until the glass had been turned 

 eight times, and the bell struck eight times. Thus four 

 hours had elapsed, the watch was completed, and the new 

 watch took charge of the ship. And so Tasman, in denot- 

 ing time, speaks of so many glasses in such-and-such a 

 watch : thus, three glasses in the morning watch would be 

 three half-hours past 4 a.m. — that is, 5.30. These sand- 

 glasses were made with the greatest care and accuracy. 

 The upper and lower sections were separated by a thin 

 metallic plate, perforated with a fine pin-hole, through which 

 the sand ran. The sand was carefully selected and dried — 

 iron-sand, I think, being preferred, as being a rounder, more 

 regular grain, and therefore affording the least friction. When 

 the running of this sand through the pin-hole had been ad- 

 justed and timed the whole was hermetically closed by lash- 

 ing, and was further protected by a wooden framework. Now, 

 it is quite possible, and not unlikely, that, conjointl}' with dead- 

 reckoning, Tasman took his longitude by the help of a four- 

 hour glass of this description, set agoing at noon when about 

 to leave port. Of course, there would be some error, due to the 

 expansion or contraction of the glass, or to failure in turning 

 at the exact moment when the last grains of sand had disap- 

 peared. Still, with all faults, this was the only method of 

 securing any reasonable approach to a fixed meridional time. 

 If Tasman did not adopt it, then his only other way of esti- 

 mating his daily longitude was by means of dead-reckoning — 

 that is, by reckoning the number of miles sailed over an east 

 or west course in twenty-four hours. This rough method has 

 been used by sailors for centuries, and is used at the present 



