March 29, 1877] 



NATURE 



471 



table or diagram as given below, in which T is a thermometer, 

 C C and c' c' are curves drawn after testing the chronometer. For 

 an ordinary voyage in which no extremes of temperature are ex- 

 pected, or which, if they occur, will be of short duration only, we 

 should seal the diagram under the thermometer, so that the tem- 

 perature line of 65° should coincide with and pass through the 

 apex of the curve, and if the chronometer were neither gaining 

 nor losing at 65° we should draw the curve as c c ; if the chrono- 

 meter were gaining five- tenths of a second per day we should 

 draw the curve as c' c'. 



Then the rate Is always to be reckoned from the summit of 

 the mercury horizontally till the line meets the curve ; if this 

 line should be to the left of the thermometer the time should be 

 reckoned z.% plus ( + ) or gaining ; if to the right, as viinus ( -) 

 or losing. 



Thus, for example, taking the line s a for a chronometer 

 whose rate at 65° is o"-oths, this will give at 75° — o"-5ths, or 

 losing half a second daily ; or for a chronometer whose rate at 

 65° (c' c') is fast o" 'Sths, at 75° it would be o" "oths for a chrono- 

 meter whose daily coefficient gives a curve as here drawn. 



Of course in determining a daily rate, two or more observa- 

 tions of temperature should be taken, so as to give a mean tem- 

 perature point from which to reckon the rate, as the day and 

 night temperatures differ considerably. 



Prof. Lieusous, in his brochure, gives a rule for determining the 

 amount which a new chronometer is likely to gain on its rate, 

 owing to the hardness of the balance- spring and other causes in- 

 dependent of temperature, but we do not find this latter so 

 reliable as the temperature-correction method as detailed above. 



Should this prove interesting to your readers, we may, with 

 your permission, at some future time give a few reasons for the 

 difference that is found to exist between the daily coefficients of 

 temperature of different chronometers. 



Parkinson and Frodsham 



4, Change Alley, Cornhill, London, March 12 



P.S. — The above system renders the auxiliary compensation 

 unnecessary, and can therefore effect a saving of 4/. to 5/. on the 

 cost of each instrument. 



Lowest Temperature 



There appears to be something almost abnormal in the 

 climatic conditions to which the observatory at Stonyhurst is 

 subject (vol. XV. p. 399). I remember going into a garden in 

 the neighbourhood of Knaresborough, in Yorkshire, about eight 

 o'clock on the morning of Christmas Day, i860, and seeing 

 what I suppose had never been seen in England outside a labora- 

 tory before that morning, viz., the mercury in a thermometer 



standing at 8° F. below zero, i.e., 40^ F. of frost. At Stony- 

 hurst on the same day the thermome'er went down only to 6° 7 

 F., i.e., there were 25° '3 F. of frost. 



Again, on March i, 1877, the lowest temperature registered 

 in the neighbourhood of Knaresborough was only, I believe, 

 18° F., whilst at Stonyhurst it was <f'i F. The differences, 

 therefore, between the temperatures on the two days spoken of 

 at these places, not fifty miles distant from each other, were 

 respectively 2'="4 F. and 26" F., which are so wide apart as to sug- 

 gest that Stonyhurst is subject to climatic conditions which do not 

 prevail in the Vale of York. I may mention that the record in 

 the Times of the temperature on the morning of March i, was 

 only 25° F., but in country districts in the south of England it 

 was as low as 20° F. Great numbers of oaks, laurels, and other 

 evergreens were killed in Yorkshire by the frost of i860. 



Oxford R. Abbay 



Meteor 



A FEW minutes before 10 o'clock on Saturday night I saw a 

 very beautiful meteor towards the western horizon. The meteor 

 passed obliquely downwards towards Orion's belt, moving slowly 

 from right to left. When first seen it was a brilliant white body 

 about ^th the apparent diameter of the moon. As it passed on- 

 wards it became bluish and pear-shaped with a bright track. 

 Before its final disappearance between the belt and the pleiades 

 it had a purplish hue. It was visible about four or five seconds, 

 and during that period it traversed about ten or fifteen degrees. 



Brighton, March 12 W. Ainslie Mollis 



I saw the meteor at gh. 56m. p.m. of Saturday, March 17, 

 mentioned by your correspondent, " W. M." I was on the 

 sea-shore at Rossall, near Fleetwood, and while looking out to 

 sea, due west, I became aware of a sudden outburst of light on 

 my left. On turning I saw the splendid meteor sailing rather 

 slowly across the sky from a point about 3° north-west of e 

 Ilydrse to a point in Monoceros, whose position I should esti- 

 mate to be about R. A. = 7h. 30m. ; Decl, = 20° o' south. 



March 26 J. II. 



DR. SCHLIEMANN ON MYCEN^ 



LAST Thursday night will be always regarded as a 

 memorable one in the history of the Society of 

 Antiquaries, when Dr. Schliemann described to an un- 

 usually distinguished audience his own and his wife's 

 explorations on the site of the Acropolis of ancient 

 Mycenae. Taking as his clue the well-known passage in 

 which Pausanias (A.D. 176) speaks of the ruins and tradi- 

 tions of the famous Greek city, Dr. Schliemann was led 

 to the belief that his scholarly predecessors had mistaken 

 its drift. The passage in Pausanias runs thus : — 



" Among other remains of the wall is the gate, on which 

 stand lions. They (the wall and the gate) are said to be 

 the work of the Cyclopes, who built the wall for Paetus in 

 Tiryns. In the ruins of Mycense is the fountain called 

 Perseia, and the subterranean buildings of Atreus and his 

 children, in which they stored their treasures. There is a 

 sepulchre of Atreus, with the tombs of Agamemnon's 

 companions, who on their return from Ilium were killed 

 at dinner by ^gisthus. The identity of the sepulchre of 

 Cassandra is called in question by the Lacedaemonians of 

 Amyklae. There is the tomb of Agamemnon and that 

 of his charioteer Eurymedon. Teledamos and Pelops 

 were deposited in the same sepulchre, for it is said that 

 Cassandra bore these twins, and that, when still little 

 babies, they were slaughtered by ./4Lgisthus, together with 

 their parent. Hellanikos (b.c. 495-411) writes that 

 Pylades, who was married to Electra by the consent of 

 Orestes, had by her two sons, Medon and Strophios. 

 Clytemnestra and .^gisthus were buried at a little dis- 

 tance from the wall, because they were thought unworthy 

 to have their tombs inside of it, where Agamemnon re- 

 posed, and those who were slain with him," 



Previous explorers had searched in vain for any of the 

 relics here referred to, because they searched in the wrong 

 place, mistaking the wall spoken of for that of the city, 



