NA TURE 



[April 15, 1909 



the centre. The third screw is midway between the other 

 two, and at the end of the plates. 



Looking normally through the plates at the glowing 

 filament of an incandescent lamp, a number of images 

 of it will probably at first be seen. Adjust the pressure 

 screws until these images are in juxtaposition in the line 

 of sight ; the silvered surfaces are then approximately 

 parallel. Place the instrument in a clamp stand, and 

 focus the light from a sodium flame or a vacuum tube 

 upon the plates, and look at the interference bands with 

 a small laboratory telescope focussed for infinity. Usually 

 the eye-piece has too large a magnification for the above 

 retardation, and it is better to use in place of it a single 

 lens of focal length about 2 inches. At first only a small 

 section of the interference pattern is seen, but with a 

 little careful adjustment of the pressure screws the whole 

 ring system is obtained in sharp focus. Removing the 

 telescope, and with the above lens used as eye-piece, focus 

 the interference system from the above sources, or an arc 

 upon the slit of a spectroscope. The bands in the different 

 spectrum lines are thus observed with the telescope on the 

 spectrometer. 



For further suggestions regarding the adjustments and 

 other experiments for which this apparatus can be used 

 reference may be made to an article by the writer in the 

 Philosophical Magazine for May, 1904. 



James Barnes. 



Bryn Mawr College, Bryn Mawr, Pennsylvania. 



An Ornithological Coincidence. 



On September i8, 1908, a fine, typical male of Anthus 

 bertheloti, Bolle, the common Canary Islands pipit, was 

 caught near Cremona, the first of its kind obtained in Italy. 

 I received the interesting specimen "in the flesh." On 

 March 16 of this year Mr. W. P. Pycraft presented at the 

 meeting of the Zoological Society of London an account 

 of the fossilised remains of a small Passerine bird from 

 the " Gabbro " (Lower Pliocene) near Leghorn, which he 

 identified as those of Berthelot's pipit (see Nature, p. 119). 

 The coincidence is certainly worth noting. 



I may add that last autumn, during the later migra- 

 tions, we had in Italy an unusual inflow of western species 

 of birds, and amongst others and the above-mentioned 

 pipit I received, also " in the flesh," a fine specimen of 

 the large variety of the wheatear (_Saxicola leucorrhoa. 

 Cm.), known to breed in Greenland and to migrate south- 

 wards along the extreme west of Europe into Senegal. 

 The specimen, a female, is the first registered in Italy ; it 

 was captured, also near Cremona, on November 7 last. 

 Henry H. Giglioli. 



Royal Zoological Museum, Florence, March 29. 



April Meteors, 



Moonlight will not hinder observations of the Lyrids 

 and other shooting stars in the latter part of April in the 

 present year. The following are the principal meteor 

 showers that become due during the period April 19-30. 

 The times of the various meteoric events as calculated 

 by the writer are expressed in Greenwich mean time. 



Epoch April 19, I2h. Shower of eighth order of magni- 

 tude, the maxima of which occur on April 20, loh. 4Sm., 

 22h. 30m., and April 22, 6h. There is also another smaller 

 shower connected with this having its maxima on April 20, 

 I2h., April 21, i8h., and April 22, 7h. 



Epoch April 25, ih. This shower, which is of the thir- 

 teenth order of magnitude, has its principal maximum on 

 April 27, I4h. Secondary maxima take place on April 25, 

 i4h. 30m. and 2oh. 30m. 



Epoch April 29, i8h. Shower of seventh order of 

 magnitude. Its principal maximum occurs on April 27, 

 gh. 45m., and there are other maxima on April 27, 

 23h. 45m., and April 29, 3h. 



From the foregoing it seems that meteors should be 

 found especially numerous on the nights of April 20 

 and 27. On the latter night there are two principal 

 maxima occurring at times very suitable for observation. 



April 12. John R. Henry. 



XO. 2059, VOL. 80] 



THE GRAMOPHONE AS A PHON AUTOGRAPH. 



IT is well known that during the last few years the 

 gramophone (invented by Berliner in 1887), in 

 its more complete and expensive forms, has been 

 so much improved as to have completely eclipsed 

 the phonograph. It is now an instrument that not 

 only records pitch and intensity, but also quality to 

 a surprising degree, so that one can listen to 

 orchestral music in which the quality of each musical 

 instrument is rendered witli much fidelity, and also 

 to the fine voices of many of the most celebrated 

 vocalists of the day. Chorus effects are also remark- 

 able, and one can, for example, enjoy the Soldiers' 

 Chorus from Faust or the Wedding Chorus from 

 Lohengrin. The nasal effects, the thin reediness of 

 the voices, the alterations in quality, so characteristic 

 of the phonograph, and of the gramophone in its 

 earlier stages, have now almost entirely disappeared; 

 indeed, it is no exaggeration to say that no scientific 

 instruments have made greater progress since the 

 inception of the phonograph a little more than thirty 

 years ago. 



Certain interesting data regarding the gramophone 

 disk are worth recording. These I have determined 

 on one of the smaller disks having a diameter of 

 105 inches, with the record beginning 3 inch from 

 the margin. The record then traces its spiral groove 

 until it is 2j inches from the centre, so the record 

 has a breadth of a little more than 2| inches, or, say, 



3 inches. The diameter at the beginning of the 

 record is 10 inches, in the middle 7 inches, and at the 

 close of the spiral, towards the centre of the disk, 



4 inches. Multiplying each by 3' 14 gives the circum- 

 ference of the circle as 3i'4 inches, in the middle 

 2198 inches, and in the centre i2'56 inches, or, 

 together, 6594 inches, giving a mean of 2r98 inches, 

 or, say, 22 inches. There are 100 grooves per inch 

 from the centre towards the circumference ; 

 100x22 = 2200 inches; the breadth of the record 

 = 3 inches; therefore 2200x3 = 6600 inches; or 

 550 feet, or 183 yards, is the average length of the 

 record groove. That is to say, in reproducing 

 Waldtenteufel's waltz, Estudiantina, the needle, in 

 205 seconds, ran over a distance of 550 feet. This 

 gives a rate of 32'2 inches per second. With disks 

 of a larger diameter, the length the groove in a 

 long record may be more than 200 yards. 



But when this record was reproduced (it is a re- 

 markably good orchestral record) the disk travelled at 

 the rate of 76 revolutions per minute, or o"S second 

 per revolution. At the beginning of the record, 

 therefore, i inch was covered in 3/100 second, at 

 the middle in 4/100 second, and at the close of the 

 record in 6/100 second. In other words, the needle 

 traverses a shorter and shorter distance, but in the 

 same time, in passing from the circumference to 

 the centre. Consequently there is no alteration in 

 pitch. It follows also that, given vibrations of the 

 same frequency for a note sounding at the beginning 

 of the record and at the close, the marks of each 

 vibration must be closer together at the centre than 

 at the circumference. Thus, supposing a frequency 

 of 200 per second, there would be about six vibrations 

 in an inch at the beginning (outer circumference) and 

 twelve in an inch at the end of the record (centre). 

 A note of 1000 vibrations per second would have thirty 

 in an inch at the beginning, and sixty in an inch at 

 the close of the record. I was able substantially 

 to verify this by placing the disk under a micro- 

 scope, with a low power, and counting the number 

 of marks in a lineal inch. This also gives a con- 

 venient method of determining the pitch of any note, 

 provided one can count a sufficient number of marks 



