July 3 i, 1884] 



NA TURE 



ment is conducted so that during the dilatation of the 

 air in A and Aj the index of the differential thermometer 

 ■y, which combines both instruments, is kept const, ait. 

 Suppose then a beam of heat rays to fall upon a thin piece 

 of platinum foil ' in A through the glass -wall. The im- 

 mediate effect of radiation is to elevate the temperature 

 of the air in a, but as an increase of only o'ooi6 of a 

 centigrade causes a displacement of the differential index 

 y of 1 mm./ it is easy for the operator to compensate this 

 tendency and transform the heat into work by lowering 

 the graduated tube D, which makes the air in a and A; 

 expand. This expansion is isothermic in both, because 

 volume and pressure varies in the same way in A as in A„ 

 where it, as shown formerly, follows Mariotte's law. 3 The 

 rate of expansion of the air is indicated by the rise of the 

 mercury in the calibrated tube D. The sensibility of the 

 differential index is so great that it requires a very steady 

 hand to regulate the movement of D so that the index 

 keeps constantly at its initial point, without making 

 greater excursions to either side than 1 or 2 mm. Every 

 irregularity in the movement changes the isothermic ex- 

 pansion into adiabatic dilatation or compression. I 

 therefore prefer to regulate the sinking of D by means of 

 a screw. During the experiment A must be protected by 

 isolating screens, &c, from outward disturbing thermal 

 influences. I think I have realised this in a satisfactory 

 way, but as a detailed account of the arrangement would 

 be too long, I must reserve the complete description for a 

 future paper. 



Lastly I will mention some examples of determinations 

 of the radiant heat emitted by a regulation gas-burner at 

 22'5 cm. distance from A. The radiation was admitted 

 through a screen with an opening of 4.5 X 2g cm. The 

 initial volume of the air in a 4 was 622'22 c.c. The pres- 

 sure was brought to 760 mm. Experiment I. was made 

 at noon, II. in the afternoon of the same day. 



Experiment I. — Increase of volume by expansion during 

 6 minutes = 1 85 '9 c.c. Mechanical equivalent of the 

 radiation during 6 minutes = I '680 M.K°. Mechanical 

 equivalent of the radiation during 1 minute = o'2So 

 M.K°. 



Experiment II. — Increase of volume, &c, during 5 

 minutes = 1 58^5 c.c. Mechanical effect of radiation in 5 

 minutes = I '459 M.K°. Mechanical effect of radiation in 

 1 minute = cr29i M.K°. 



I have measured in this way the mechanical effect of 

 radiations, the caloric energy of which was only o'o8 of a 

 gramme-calorie in the minute. This method is free from 

 every kind of correction. It is obvious that, by means of 

 a thin test-tube hermetically inserted into A, calorimetric 

 determinations of specific heat, &c, could be made, but I 

 have not yet arranged the apparatus for this purpose. 

 Otto Pettersson 



Stockholms HSgskolas Laboratorium, June 25 



NOTES 



The Government have directed Dr. Klein, F.R.S., and Dr. 

 Heneage Gibbes, to proceed to India to pursue a scientific inquiry 

 into the nature of cholera. It is understood that these gentlemen 

 will act in conjunction with the Commission nominated a few 

 weeks ago by the Indian Government for the same object. 



At the meeting of the Council of the Marine Biological Asso. 

 ciation on Friday, July 25, Prof. Moseley in the chair, the names 



} It is blackened in the following way. It is galvanically coated with a 

 thin layer of metallic copper, and afterwards heated in a current of oxygen. 

 This arrangement gives most sensitive indications. 



This is the case in the apparatus constructed by the author. The index 

 there consists of a small drop of coloured alcohol. If H a SO.j is substituted for 

 the alcohol, the sensibility of the apparatus is lessened considerably. 



3 In my last constructed apparatus I have substituted a vessel of thin 



copper instead of the upper part of the glass vessel A,. This arrangement 



answers the purpose excellently. 



♦ And also in a„ which is of the same size. This condition is, however, by 



indispensable. A, can be greater or smaller than A, only the 



B and Cj are proportional to each other. 



dimensions of A 



of Prof. Allman, F.R.S., and Sir John St. Aubyn, Bart., M.P., 

 were added to the list of Vice-Presidents, and Mr. Spence Bate 

 of Plymouth was elected on the Council. It was decided that, 

 provided certain arrangements promised by a committee of the 

 Town Council of Plymouth were carried out, the Association 

 should proceed to erect its first laboratory on Plymouth Sound. 

 Plymouth is not only the best position for the laboratory on 

 account of its natural features, but the local committee has 

 offered to the Association a free site on the seashore and a sub- 

 scription of 1000/. A vote of thanks to H.R.H. the Prince of 

 Wales for having become the Patron of the Association was 

 carried. The financial prospects of the Association were reported 

 as highly satisfactory. The building of the laboratory will 

 probably be commenced in the spring. 



The eighth International Medical Congress is to be held in 

 Copenhagen from August 10 to 16. President, Prof. Dr. P. L. 

 Panum ; Secretary, Dr. C. Lange, both of Copenhagen. Among 

 the most eminent of the 658 medical men who have engaged to 

 attend are :— Prof. Lister, Sir William Gull, Bart., Prof. Dr. L. 

 Pasteur, Prof. Paul Bert, and Prof. Dr. R. Virchow. 



The Congress of the British Medical Association opened in 

 Belfast on Tuesday. Prof. Canning directed his presidential 

 address mainly to an analysis of the origin ami causes of the 

 spread of epidemic diseases. 



The prospectus has just been issued of the new " Societa. di 

 Geografia ed Etnografia," founded in Turin in anticipation of the 

 Italian Geographical Congress, which meets in that city on 

 August 15. The Congress is a passing event, but the Society 

 has probably a brilliant career before it, established as it is under 

 the auspices of Prof. Guido Cora, its first President. The well- 

 known Cosmos of the distinguished geographer becomes the 

 authorised scientific Journal of the Society, a happy arrange- 

 ment which cannot but prove mutually beneficial. In other 

 respects everything is for the present provisional, and the council, 

 including besides Sig. Cora such names as those of Luigi, Schia- 

 parelli, Enrico Morselli, and Alessandro di Cesnola, holds office 

 only till the beginning of next year, when the statutes will be 

 definitely settled, and a permanent administration established. 

 Meantime it is satisfactory to find that ethnology, a branch of geo- 

 graphical science so strangely neglected by existing geographical 

 institutes, is to receive all due prominence and encouragement. 

 Another important feature is the attention to be paid to com. 

 mercial and industrial geography, especially as regards I taly in 

 its relations with foreign countries. This idea also, mutatis 

 mutandis, might be advantageously adopted by similar learned 

 bodies elsewhere. 



The Boltettino of the Italian Geographical Society for July 

 publishes the circular, regulations, and programme of the first 

 Italian Geographical Congress, which meets in Turin from the 

 15th to the 19th of next August under the presidency of the 

 President of the Italian Geographical Society. All except 

 honorary members to be specially named will be expected to 

 contribute towards the expenses sums varying from ten to thirty 

 francs. In return they will have free access to all the scientific 

 gatherings, and will be entitled to a copy of the Proceedings of 

 the Congress. There will be two Sections — a Scientific and 

 Commercial, and questions will be discussed in connection with 

 mathematical, physical, ethnographic, political, economic, and 

 historic geography. Amongst the subjects proposed for dis- 

 cussion are the following : — "What ethnological conclusions are 

 to be drawn from the more recent anthropological and philo- 

 logical data, regarding the indigenous populations of East 

 Africa?" "Considering the part already taken by Italy in 

 scientific exploration in the Polar seas, what are the best means 

 of organising an independent Italian expedition to the Antarctic 

 regions?" " On the need of preparatory schools for training 



