1 72 Proceedings of the Royal Society of Victoria. 



behav^es in a most eccentric manner, and tliat its variations 

 are but very slightly indicated by the air pump test made at 

 the Observatory on 20th December, 1S94. The \\ inch aneroid 

 worked very much better, Init did not behave as it did under 

 the air pump, whilst the 2^7 inch aneroid shows very well with 

 the exception of one discordant observation, and its behaviour 

 is very similar to what it was under the air pump. 



Taking the whole of the results they fully justify (so far as 

 they go) Mr. Edward Whymper's conclusion, " that the test which 

 is usually applied of comparing for brief periods (minutes or 

 hours) aneroids with mercurial barometers under the air pump 

 is of little or no value in determining the errors which will 

 appear in aneroids used at low pressure for long periods (weeks 

 or months)." — " How to use the Aneroid," page 9. 



The behaviour of the small bore Mountain mercurial is at tirst 

 sight very peculiar, but is, undoubtedly, due to varying capillary 

 action in the small instrument. No measurements of the heights 

 of the meniscus were taken, but it was apparent that these were 

 continually varying both in upper and lower limbs though 

 principally in the latter where the meniscus at times entirely 

 disappeared, and at other times exceeded considerably that in the 

 upper limb. In every case the instrument was well tapped prior 

 to taking a reading. It would appear that the readings of this 

 barometer could be depended on to about 0*03 inch, and the 

 error would be independent of altitude. 



The boiling-point experiments resolve themselves into two 

 sections, one taken with a glass spirit lamp, which was not 

 .sufficiently powerful to maintain a good supply of steam, and the 

 otlier with a brass lamp which generated steam with ease. As 

 might be expected the boiling points given l)y the former are all 

 lower than those given by the latter. (^ne of the observations 

 (that on the 26th August, 4 p.m.) should undoubtedly be rejected, 

 as the apparatus was at the time undergoing alterations and 

 consequently tlie bull) was exposed to a mixture of air and steam 

 instead of pure steam. Taking the second set of observations 

 (sixty-seven in number), the maximum difference in the correction 

 to standard is 0'048 inch as against 0*068 inch witli the 

 Mountain mercurial. 



