DISCUSSION-OSCILLATION OF THE ATMOSPHERE 1 0 5

spheroidal configuration. The gravitation would tend to restore the spherical form, but on account of ,the momentum acquired by the time this form was reached the globe would oscillate a b u t the spherical form, alternately being slightly prolate and oblate. In the case of the a t m o s pheric oscillations the axis of this spheroid is in the equatorial plane, and is fixed relative to the sun; consequently it rotates to westward with the sun relative to the earth. The actual atmospheric particles d o not travel round the earth, of course; they oscillate nearly horizontally, their range being about six kilonietres. On ‘this amount the disturbing influence of a mountain is likely to be confined within a moderate multiple of this distance from the mountain. -\s regards Mr. \Vhipple’s question about pressure and mass in the barometer, the tidal variation of vertical gravity due to the sun and m a n is too small to have an appreciable influence on the rending of a barometer. -1s regards the 5-hour term he was aware that i t showed great regularity in the British Isles and he would like to consider it dynamically, but so far as he knew meteorologists have not paid as much atten.tion to that oscillation as they have to the Iz-hourly one and he did not know where to get collected data for a large part of the earth. With reference to the variation of the semi- diurnal oscillation throughout the seasons from the equinoxes to the solstices, it is not necessarily due to the change in the mean temperature; it will also be affected by the obliquity of the earth’s asis. .4s regards computing the friction of the earth’s atmosphere from this oscillation, he did not feel hopeful about it. One would need to have a more exact division between the thermal and tidal parts of the phenomenon. Con- cerning Dr. Chree’s remarks about the barometer a t Kew Observatory, he did not think such variations of temperature in a room aould be likely to have a lunar period and hence he did not contemplate comparing the lunar tide of two places so close together as Kew and Greenwich. H e noted what Dr. Chree said a b u t the confidence in the lunar atmospheric tide a t Mauritius owing to the calculation of two periods separately. Unless one can get some comparison between results from different periods one cannot have confidence in the result and he had borne that point in mind.

CORRESPONDENCE AND NOTES. As Others See Us.

The following extract, written by Edgar -4. Griffiths, is from the Iountal of Scientific Instrrments, Vol. I , No. 3 , p. gj , and is part of a review on the recently published “ Dictionary of ApfiZied Physics.” Perhaps Fellows of the Society may have views of their own on the subject of meteorological instruments and meteorological observntions and would like to forward them for publication in the ]oicrrinZ.

“ The article on ‘ Meteorological Instruments ’ in Volume 111. [of the Dictionary] by Mr. Corless affords an insight into the present position of this subject. The writer remarks : ‘ Amateur observers must always form the great majority of contributors to the whole stock of observational data and most of them are not trained physicists or skilled mechanics.’ This argument is used to justify the com-

I@ COKKESPOSDENCE AND NOTES

paratively crude instruments cmployed in this science. We venture to think that, if serious attention were given to the question of making the study of meteorology really attractive, the subject might appeal to amateurs of the type that now encounters no unsurmount- able dificulties in grappling with the intricacies of wireless apparatus. The experimenter must be provided with apparatus whioh is sound in principle and interesting to use, for what can be more depressing than, for example, to be asked to make observations of solar radiation with a Stokes-Campbell glass ball and a black bulb in vacuo (SO-

callcd) or of hummidity with an unventilated type of wet and dry bulb hygrometer ? ”

“ A s Others See Us.” A Reply from the Writer of the Article in the Dictionary.

Mr. Grifiths would have us use “ interesting ” instruments like wireless receivers, and thinks observers could even make their own instruments, just as everybody now makes his o\vn nireless receiver. He \vould :ipparrntly havv us rcgard our instrutnents at the norst as playthings, and a t the best as experiniental apparatus.

Can he mine a single ship of which the wireless apparatus provided for the purpose of facilitating regular and serious coinmunicntions h a s been constructed by the wireless operator himself? Routine observations to be of scientific value must always be made by apparatus ahich coni- bines simplicity and strength with accuracy, uniformity and reliability. Such is emphatically not the character of most of the \virclcss receivers built by the “ man-in-the-street ” for purposes of recreation. Our kno\v- lpd& of the metcorology of the globe is considerable, though still wry far from being complete, yet it \vould not have been nearly s o advanced as it is had it not been derived from observations made o.ith simple but not inaccurate instruments.

Mr. Grifiths appears not to be aware that a sunshine recorder \vas designed to give, and actually gives, satisfactorily, not the intensity of radiation, but the duration of sunshine.

May I suggest that IMr. Gyiffiths (or other interested reader) should design a n instrument for measuring the intensity of solar radiation which nould be a t once simple, reliable, accurate and not too espensive? Of “ intcrrsting ” instruments for this purix>se \ve have ;I number’ already in use a t our observatories, but they are too complicated for general use. .in instrument of this type is much required a t the present time to take the place of the muchdespised solar-radiation thermometer, which by the way has not, I believe, received all the attention which i t deserves. R. CORLESS.

Reader in Electrical Meteorology.

re-appointed Reader in Electrical Meteorology.-Nature, June 14, rgq. kIr. C. T. R. Wilson, Sydney Sussex College, Cambridge, has been

* Including the Angstriim pprheliometer, the Abbott silver disc pyrheliometer, the llichelsen pyrheliorneter, the Callendar radiation recorder.