344 



NATURE 



\Fcb. 29, 1872 



Hall, not only gave up the use of his yacht for the 

 summer in the cause of Science, but bore nearly the 

 whole expense of the cruise himself. The naturalist who 

 accompanied them was Mr. Kent, of the British Museum, 

 a man comparatively unknown before that time ; and 

 this was, perhaps, the reason why the Royal Society 

 could only afford to give ^50 towards the txpense of ap- 

 paratus, &c. As a natural consequence, the expedition 

 was considerably crippled for want of proper gear, and 

 they were unable to attempt deep-sea work. It is too 

 rare for persons who are blessed with means to assist 

 Science in any way, and when such an act of generosity 

 does take place, it ought not to be forgotten on the part 

 of the scientific public. Yet it is rumoured that a similar 

 expedition to Morocco and Madeira, which Mr. Marshall 

 Hall is arranging for the spring, is likely to be received 

 with some coldness by some influential members of the 

 scientific brotherhood. We sincerely hope that the 

 rumour is incorrect. 



It appears that Mr. Marshall Hall proposes to be 

 absent from England for between three and four months ; 

 and, besides the natural history, to investigate, as far as 

 possible, certain chemical and physical questions concern- 

 ing the deep sea and its currents in the neighbourhood of 

 the above-mentioned places. He is taking with him a 

 young naturalist, Mr. P. T. Abraham, B.A., B.Sc, lately 

 from Dublin, at which University he came out first in 

 natural science honours, and where he has gained a high 

 reputation for zoological knowledge. It is also probable 

 that another naturalist will make up the staff. These 

 gentlemen intend to give, besides the use of the yacht, 

 150/. or so — as much as they are able. The remaining 

 250/. — for the total cost of the expedition could not 

 amount to much less than 400/., when the items of gear, 

 apparatus, outfit, and maintenance for such a time are 

 taken into consideration — they hope to obtain in the form 

 of grants from the learned societies. We feel sure that 

 the Royal Society will be among the first to .endow the 

 work out of the fund placed at their disposal by the 

 Government, and the best friends of Biology may wish 

 that they had more frequent opportunities atforded them 

 of assisting in researches in which it is fitting that in the 

 first instance a private individual should come foiward. 



It is possible even that other societies may be induced 

 fo help if they have funds at their dijpasal. Among 

 such societies we may mention the Zoological Society, 

 which contains on its roll the names of men of the first 

 rank in every department of zoology. It is true that a 

 great portion of the funds are expended in the direction 

 of the higher vertebrates, and that the lower animals do 

 not receive the attention they may deserve ; but still, it 

 must be remembered that the great object of the society is 

 the popularisation of natural history. 



We hope that the Nonids will not be the only dredging 

 excursion starting from British waters this year. The 

 field that has been so ably opened up by Dr. Carpenter 

 and his colleagues ought not to be allowed to slip away 

 altogether from the hands of Englishmen. We know too 

 well that other nations are not backward in following up 

 and eclipsing the work that British pluck and genius have 

 been the first to venture upon. The Americans are on 

 the track, and our Continental neighbours will not be far 

 behind. 



We are glad that the extended circumnavigation expe- 

 dition is in process, and we believe that if nothing un- 

 forseen occurs. Prof. Wyville Thomson, with a staff of 

 competent aids, will sail in the autumn on their long 

 journey, which cannot fail to have the most important 

 bearing on our future advance in such studies. Such a 

 journey as this, however, instead of making more modest 

 dredging operations of no avai', vistly ini reas s their in- 

 poitance ; and it is not too muLfi to hope that the time is 

 not far distant when men of money and leisure will more 

 generally occupy their time in such pursuits. 



SOLAR HEAT 



'T'HE calculations presented by Pcre Secchi, in his 

 -*• work " Le Soleil," relative to solar temperature and 

 solar radiation, tending to discredit the result of recent 

 investigations on the subject, I have carefully examined 

 the " solar intensity apparatus," the indications of which 

 form the basis of those calculations. This unique device 

 will be found delineated on p. 267 of the work referred to, 

 the accompanying illustration (Fig.ji) being a fac-simile of 

 the same. It represents a longitudinal section through 

 the centreline, thus described : — A B and C D are two 

 concentric cylinders soldered one to the other ; they form 

 a kind of boiler, the annular space being filled with water 

 or oil at any temperature. A thermometer, /, passes 

 through a tube, across the annular space, to the axis of 

 the cylinder ; it receives the solar rays introduced through 

 a diaphragm, m n, the opening, 0, of which is very little 

 larger than the bulb of the thermometer. A thick glass, 

 V, closes the back part of the instrument, and admits of 

 ascertaining whether the thermometer is placed in a direct 

 line with the pencil of rays. The interior cylinder and 

 the thermometer / are coated with lamp black. A second 

 thermometer, /', shows the temperature of the annular 

 space, and consequently that of the inclosure. The whole 

 apparatus is mounted on a support having a parallactic 

 movement, to facilitate following the diurnal motion of 

 the sun. The apparatus being exposed to the sun, it will 

 be found, on observing the two thermometers, that their 

 difference of temperature increases gradually, and that in 

 a short time it ends by being constant. 



Before pointing out the peculiarities of the contrivance 

 thus described by Pere Secchi, it will be instructive to 

 examine his " solar intensity apparatus," manufactured by 

 Casella, represented in Fig. 2. The manufacturer pub- 

 lishes the following statement regarding this instrument : 

 — " Two thermometers are here kept immersed in a fluid 

 at any temperature, and a third surro'inded by the same 

 conditions, but not immersed, is exposed to the rays of 

 the sun. The increase of temperature thus obtained is 

 found to be the same, irrespective of the temperature of 

 the fluid which surrounds it." No one acquainted with 

 the prii ciples which govern the transmission of heat 

 within circulating fluids can fail to observe that the ther- 

 mometers applied above the central tube will not furnish 

 a reliable indication of the temperature of the fluid below 

 the same, nor of any portion of the contents of the annular 

 space towards the bottom. Apart from this defect, it will be 

 perceived that an upward current of atmospheric air will 

 sweep the underside of the external cylinder, causing a re- 

 duction of temperature of the fluid confined in the lower half 

 of the annular space. Again, the heat radiated by the 

 bulb of the thermometer exposed to the sun will elevate 

 the temperature of the air within the central tube, and 

 consequently produce an internal circulation tending to 

 heat the upper part of the fluid contained in the annular 

 space. The effect of the irregular heating and cooling 

 thus adverted to will be considered after an examination 

 of the result of some observations recorded in Table A 

 conducted at different times during the month of Sep- 

 tember 1871. In order to insure an accurate position, the 

 instrument during these observations was mounted in a 

 revolving observatory upon a table turning on declination 

 axes provided with appropriate mechanism and declina- 

 tion circle. An actinometer being attached to the same 

 table, the true intensity of the radiant heat, as well as the 

 sun's zenith distance, were recorded simultaneously with 

 the indications of the Secchi instrument furnished by 

 Casella. Let us first consider the tabulated observations 

 of September 2 recorded at equal intervals of three 

 minutes. The indication of the two thermometers 

 immersed in the fluid contained in the annular space first 

 claims our attention, since the temperature of this fluid is 



