Aug. 3. 1876] 



NATURE 



297 



M. Saleron made an experiment suggested by M. 

 Ledieu, and which is a consequence of the fact above 

 mentioned. If the light is received alongside the axis, 

 the radiometer rotates. The velocity of the rotation is 

 not yet in our hands. 



The reflection of the light on the glass creates a dis- 

 turbing force, as it is easy to show by the following experi- 

 ment, which I made before the Academy of Sciences : — 

 The bulb of an ordinary radiometer being half blackened, 

 the rotation takes place in the same direction, whatever 

 be the position of the blackened hemisphere, but at diffe- 

 rent rates. With the light falling on the white side, the 

 rotation is reduced to about \, and about f when falling on 

 the blackened side. Both numbers give exactly i, i.e., the 

 regular number of the translucid sphere. Consequently, 

 I suppose the reduced rotation to be produced by the 

 light reflected on the glass by the blackened surface, 

 which light adds its effects to the light falling directly on 

 the said blackened surface. This theory is in conformity 

 with the well-known fact as stated by Crookes, that light 

 A + light B gives one effect A -f B, whatever be the 

 respective situation of the lights on the circumference of 

 a circle whose centre is the radiometer. I have no doubt 

 that, by silvering the blackened hemisphere, which en- 

 larges the reflecting power of the interior, the velocity 

 of either rotation can be enlarged. 



These remarks explain facts that, according to the 

 dilatation theory, are a mere impossibility, the rotation 

 in the same direction when a ray of light falls on the 

 black or on the white side. These experiments can be 

 made not only with a white or a black radiometer instead 

 of alternate, but also with entirely transparent bulb, if 

 light is predominant in one direction. 



The difficulty in using the radiometer as a photometer 

 is in the velocity of the revolutions, M, Gaiffe con- 

 structed for me a radiometer with a graduated screen 

 which was in operation at La Villette Gas Works, and was 

 sent to the lighthouse experimental establishment. Un- 

 fortunately that instrument requires a heliostat to send 

 the rays into the aperture. Under that limitation the 

 instrument works well, as the scale of proportion has 

 been very easily established. 



That reduction can be tried with a greater simplicity 

 with a differential radiometer with plates differently 

 coloured, the left with blue and the right with green or 

 red. The rotation will be equal to the difference of 

 rotating power, as demonstrated by the radiometer with 

 both sides blackened. I suppose that white-blue + blue- 

 black will give almost exactly the number of white-black, 

 and that the rotating force might be so easily fragment- 

 ised. By a graduation all these different radiometers can 

 be compared with each other. 



Some of these radiometers are being constructed ac- 

 cording to my suggestion by M, Gaiffe, and will be pre- 

 sented to the Academy as soon as the aforesaid theory 

 shall have been demonstrated experimentally, 



W. DE FONVIELLE 



PROF. STEERE'S EXPEDITION TO THE 

 PHILIPPINES 



T T may interest zoologists to know that an American 

 ■^ gentleman. Prof, J. B. Steere, of the University of 

 Michigan, has recently returned from an expedition to 

 the Philippine Islands, bringing with him large collec- 

 tions of natural history objects. The birds he has sub- 

 mitted to me, and I am now engaged in preparing a 

 memoir on the collection, which seems to be one of the 

 most important ever made in the Indo-Malayan Islands. 

 In spite of the great difficulties which meet the tra- 

 veller in the Philippine group, and notwithstanding severe 

 attacks of fever. Dr. Steere exerted himself with great 

 energy, and as he visited many islands in which no pre- 



vious collection had ever been made, it is not surprising 

 that many novelties occur in the one he has now brought 

 over to England for description. 



Leaving Hongkong for Manila, in May, 1874, Dr. 

 Steere crossed the Island of Luzon by way of Mauban 

 and Lucban to the Pacific, passing some time on the 

 mountain of Ma-hay-hay, near the Laguna de Bay, In 

 July he went by steamer to the colony of Puerto Princesa, 

 on the east side of the Island of Palawan, where he stayed 

 a month. From thence he crossed to the Island of 

 Balabac and remained a month, afterwards visiting the 

 south-east corner of the Island of Mindanao, and resting 

 for a month and a half at Zamboanga and the Indian 

 village of Dumalon in the same province. The Island of 

 Basilan, lying between Mindanao and the Sooloo group, 

 was next visited, and here he stayed two weeks, after 

 which he returned to Zamboanga and thence to Manila. 

 In the month of December he again went south, stopping 

 at Ilo Ilo, on the Island of Panay, and visiting the moun- 

 tains in the interior. After a short stay at the neighbour- 

 ing Island of Guimaras he crossed over to Negros, 

 journeying on horseback round the north end of the 

 island ; thence in a native boat he traversed the sea to 

 Zebu, which he crossed, till he arrived at the town of the 

 same name, where he took horse again and rode south- 

 ward, crossing the island once more and passing over the 

 strait to the town of Dumaguete, on the Island of 

 Negros. Dr. Steere then went back to Zebu and crossed 

 to the Island of Bohol ; after passing round part of this 

 island he returned to Zebu and afterwards to Manila, 

 where he visited the Negritos on the north side of the 

 Bay of Manila, leaving finally in April for Singapore. 



Full descriptions of the new species will shortly be 

 prepared, but meanwhile I cannot avoid drawing attention 

 to one or two of the most remarkable forms, chief 

 amongst which will be the following : — 



EurylcEtnus Steerii, Sharpe. Unlike any other member 

 of the Eurylcemiace, no species of which was previously 

 known to inhabit the group. It has a grey back, white 

 collar round the neck, the head and rump deep purplish, 

 the tail chestnut ; wings black with a yellow bar across 

 the secondaries, white on the innermost ; sides of face 

 and throat black ; rest of under surface white. The 

 male differs in having the under surface purplish red, 

 Hab, Basilan. 



Phyllornis palawanensis^ Sharpe, apparently different 

 from every other Phyllornis by reason of its yellow throat, 

 green under surface, and blue-edged primaries. There are 

 other differences, but the above seems to be a combination 

 of colouring rot met with in the other species. Hab. 

 Palawan. 



Brachyiirtis Sieerii, Sharpe. Green with a black head ; 

 shoulders and a band across the rump bright cobalt ; 

 tail black ; below verditer blue or light cobalt, the throat 

 white ; centre of the abdomen black ; vent and under tail- 

 coverts crimson. Hab. Dumalon, Mindanao. 



It is, however, among the sunbirds that Dr. Steere 

 seems to have discovered the most curious novelties, as 

 will be seen from the following birds : — 



jEthopyga wrto-z/zyf^rt, Sharpe, resembles ^■E.flavostriata, 

 Wallace, from Celebes, but is larger, with a stronger bill, 

 black belly, and is at once to be told by its black under- 

 wing coverts. Hab. Negros. 



yEthopyga Sltelleyi, Sharpe, like ^. dabrii, and ^. 

 goiildicE in appearance, but without the elongated tail, and 

 distinguishable at a glance by the entirely yellow under- 

 surface, streaked on the breast with scarlet ; the throat 

 is yellow, bordered with a double moustachial line of 

 scarlet and steel blue. Hab. Palawan. 



JEthopyga pulcherrima, Sharpe, a small species, pro- 

 bably generically distinct. Above olive-green, with a steel 

 blue trontal patch, and streak over the ear- coverts ; 

 wing-coverts, upper tail-coverts, and tail, metallic steel- 

 green ; rump yellow ; wings olive ; under-surface entirely 



