( 459 ) 
the geographical longitude of G= Talang 0° 53’ 37,833 ) East of 
ie 4 2 , Bt Gadang 0°45’ 6’’,151 \ Padang, 
whence for the longitude of the West end of the base of Padang 
respectively : 6° 26’ 26/7,858 and 6°26’ 26'’,387, of which the mean 
value is 6° 26’ 26’’,373 West of Batavia, corresponding to 
100° 22’ 10//,68 East of Greenwich. 
Hence follows that the difference in longitude between Padang and 
Batavia, as determined by geodetic measures, is less by 16’’ or over 
1s than that found by chronometers. 
Probably the difference is due for a small part only to the accu- 
mulation of errors of observation in the triangulation and almost 
exclusively to the method of determination by means of chronometers. 
Physics. — “On the melting of floating ice’, by Dr. Cu. M. van 
Deventer. (Communicated by Prof. van DER WAALS). 
In what follows I shall discuss a physical fact, which though one 
of the simplest and most important of phenomena, seems to have 
escaped the attention of physicists up to now. The author asked at 
least some twenty men versed in physics after it, and not one of 
them had heard about it: many of them and specially the most 
experienced in this branch of science were not a little astonished 
at it. It is therefore not devoid of interest to discuss the faet in 
question, though the explanation can be followed even by beginners 
in physics. 
§ 1. In order to show how surprising the fact is, we put the 
following 
Problem. 
Given a tray of a certain dimension, in which water is up to a 
certain Jevel, and in which floats a piece of ice of a certain weight, 
everything at O°. Required to find: in what way will the level of 
the water be changed, when the ice melts? 
Solution : the level of the water does not change. 
$ 2. This answer may be derived as a simple application of 
the law of ARCHIMEDEs. ‘) 
If the piece of ice weighs A kg., the upward pressure is also 
A kg., and so the weight of the displaced water also A kg. As now 
the melted ice weighs also A kg., the melted mass will occupy 
1) The weight of the air is neglected in this discussion. 
