SCIENCE-GOSSIP. 



substantially made of teak. This cold-water bath 

 thus prevents any expansion of the base and 

 supports due to heat radiated from the burner and 

 the hot-water trough above ( 2 ). The method of 

 working the apparatus is as follows : the micro- 

 meters having been screwed back sufficiently far to 

 allow the maximum expansion of the bar to take 

 place freely at the highest temperature, the burner, 

 supplied with gas at both ends, is lit and the water 

 in the upper trough raised to as near boiling-point 

 as possible. When this maximum temperature is 

 attained, one micrometer is screwed in until the 

 screw comes in touch with the short glass end- 

 pieces. The other micrometer is now screwed up 

 very carefully until the hand feels that the screw is 

 just in contact with the other glass end-piece. 

 After one or two trials no difficulty is experienced 

 in screwing to just the point of contact and 

 no more ; the means of several sets of readings 

 taken to test this point differing only to an extremely 

 slight extent from the value of any one single 

 reading. The reading on this second micrometer 

 is then taken simultaneously with the temperature 

 of the water in the trough, which temperature is 

 obtained by means of a thermometer placed any- 

 where in the water ; the latter being constantly 

 stirred from end to end with any convenient stirrer. 

 The gas is then turned off, and pairs of readings on 

 the micrometer and thermometer are taken together 

 as the temperature gradually falls. 



It may at first sight be thought that there is no 

 actual need for the second micrometer, but as has 

 been above stated, the instrument has been designed 

 for actual measurements by the students them- 

 selves, especially in large laboratory classes, where 

 they work either in pairs or threes. In these cases, 

 therefore, if the two micrometers are worked, each 

 student is actually employed in taking readings. 

 It is also essential that an apparatus of this 

 description should exemplify the principle in all 

 detail, as cases have occurred with junior students 

 in which, if the second end of an expanding rod 

 abuts against a rigid support, they have formed 

 the idea that the rod only tends to expand in its 

 free direction, not all ways. 



Plotting the readings obtained as above, upon 

 curve paper, a very uniform straight line is pro- 

 duced with this apparatus, and fig. 2 represents a 

 specimen curve actually obtained for a rod of brass. 

 Calculating the coefficient of expansion from this, it 

 will be seen that the percentage error is very small. 



Considering then the practical requirements in 

 heat laid down in the syllabus of the Science and 

 Art Department, the University of London and 

 other bodies, in which the expansion of solids 



( ! ) The efficiency of the instrument almost entirely depends 

 upon the accuracy of the micrometer gauges, those used are 

 thoroughly well made, and are capable of reading to one- 

 hundredth of a millimetre. 



occur, the present apparatus should prove a very 

 useful and trustworthy adjunct. Thanks must be 

 given to Messrs. J. J. Griffin and Sons, of Sardinia 

 Street, Lincoln's Inn Fields, W.C., who are manu- 

 facturing this apparatus, and who have kindly lent 

 the above blocks for illustration. 

 (To be continued.) 



THE "OCEANA" EXPEDITION. 



\ \ 7TTH the object of exploring the intermediate 

 vertical zone of the Atlantic Ocean, the 

 " Oceana " Expedition, organized by Mr. George 

 R. Milne Murray, F.R.S., Keeper of the Botanical 

 Department of the British Natural History 

 Museum, sailed early last month. Although so 

 much has been accomplished in investigating 

 the fauna and flora of the deepest abyssal floor 

 of the Atlantic, great doubt exists as to the 

 inhabitants of the region occupying the depths 

 below 350 fathoms and above the influence of 

 the actual bottom of the ocean. In a recent 

 presidential address to the Linnean Society of 

 London, Dr. Albert Giinther, F.R.S., urged that 

 further attempts should be made to explore the 

 middle zone with specially constructed apparatus. 

 Now this is to be attempted by Mr. Murray, 

 assisted by a scientific staff, including Messrs. 

 Vernon H. Blackman, B.A., and J. Walter 

 Gregory, D.Sc, of the Museum staff ; also 

 Mr. J. E. S. Moore, Dr. Sambon, and 

 Mr. Highley, the last-named gentleman as artist. 

 The museum authorities are lending their aid by 

 granting to Mr. Murray and his colleagues the 

 necessary leave of absence. Financial assistance 

 has been contributed from various sources, such 

 as the Royal Geographical Society, the Drapers' 

 Company and the Fishmongers' Company. Mr. 

 Murray has chartered the " Oceana," which has 

 been fitted out by the Silver town Telegraph Cable 

 Company, whose officials entered into the spirit of 

 the expedition and gave every possible assistance. 

 Work was to commence at the outer edge of the 

 100-fathom line off the coast of Ireland and 

 extended for some ten degrees westward. The 

 apparatus includes sounding-lines to over 2,000 

 fathoms and a series of thirty-eight tow-nets. 

 Other observations will be made, in regard to 

 temperature, pressure and examination of the 

 floor of the ocean, so as to get the greatest possible 

 evidence of the vertical distribution of life in- 

 habiting the Atlantic in the places sounded. 



One cannot overestimate the public spirit and 

 enterprise of Mr. George Milne Murray, shown in 

 inaugurating this scientific expedition, from which 

 we trust the results may be equivalent to its impor- 

 tance. It is a satisfaction to know that the conduct 

 of the investigations is directed by men of known 

 scientific training and ability. 



