1SJ7.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



255 



(lerful telescope. Its actual operations have been for a time suspended 

 by a cause not less honourable to Lord Rosse in another character. They 

 liave been retarded, so far as he himself is concerued, by the more im- 

 mediate duties, which, as a magistrate, and as a landowner, he owed lo 

 his neighbours, his tenantry, and his country, during the late awful visita- 

 tion which has afilicted Ireland. 



Star Catalogues. 



The Catalogues of Lacaille and of the His'oire Celeste are now before 

 the world ; and with the Catalogue of our Association constitute a series 

 of most important gifts conferred on astronomy. 



Lunar Theory. 



The Astronomer Royal has done me the honour and the kindness, by a 

 paper which I have just received from him, to make me the vehicle of com- 

 municating his wisdom to you ou a most important and interesting discovery 

 of the past year : — 



" In the lunar theory a very important step has been made in the course 

 of the past year. When, near the beginning of the present century, a con- 

 siderable number of the Greenwich lunar observations were reduced by 

 Biirg for the purpose of obtaining elements for the construction of his Lunar 

 Tables, and generally for the comparison of the moon's observed place witli 

 Laplace's theory, it was found impossible to reconcile tile tlieoretical with 

 the observed places except by the assumption that some slowly varying 

 error affected the epoch of the moon's mean longitude. From the nature 

 of the process by whicli the errors of the elements are found, the conclusion 

 upon the existence of this peculiar error is less subject to doubt thau that 

 upon any other error. So certain did it appear, that Laplace devoted to it 

 one entire chapter iu the Micanique CHeste, with tlie title ' On an in- 

 equality of long period by which the moon's mean motion appears to be 

 affected.' Guided by the general analogy of terms producing inequalities 

 of long period, he suggested as its probable cause an inequality whose ar- 

 gument depends upon a complicated combination of the longitude of the 

 earth's perihelion, tlie longitude of the moon's perigee, the longitude of the 

 moon's node, and the moon's angular distance from the sun. lint he made 

 DO atlempt to calculate its theoretical efl'ect. He also suggested an in- 

 equality depending on a possible difference in the uortdern and southern 

 hemispheres of the earth. Many years elapsed before these suggested 

 theoretical inequalities were carefully examined by physical astronomers. 

 At length the introduction of new methods enabled Poisson and Lubbock 

 successfully to enter upon the investigation of Ibe theoretical values ; and 

 they proved that inequalities depending on the arguments suggested by 

 Laplace could not have sensible values. The theory was now left in greater 

 doubt than ever ; and suspicion fell even on the accuracy of the reductions 

 of the obseriations. 



" A few years since, as is well known to members of the British Asso- 

 ciation, the British Government, at the representation of the Association, 

 sanctioned the complete reduction, on an uniform plan, of all the observa- 

 tions of the moon made at the Royal Observatory of Greenwich since the 

 year 1750: and the immediate superintendence of this work was under- 

 taken by the Astronomer Royal. The reductions are now printing in all 

 necessary detail ; and the press-work is at this time very far advanced. 

 In the last summer the corrections of the elements of the moon's orbit were 

 generally obtained; and the errors of epoch in particular at different times 

 were found with great accuracy. These results coutirmed those of Biirg, 

 and extended the law of the inequality to a much later time. In this state 

 they were exhibited by the Astronomer Royal to Prof. Hansen of Gotha, 

 who was known to be engaged in the Lunar Theory. Prof. Hansen im- 

 mediately undertook a search for their theoretical causes. His perfect 

 knowledge of the state of the existing theories enabled him at once to single 

 out the class of disturbances produced by the action of the planets as that 

 in which the explanation of this inequality would probably be found. In 

 the course of a systematic search, many inequalities of long period were 

 found; but none of sensible magnitude. At length two were found, both 

 produced by the disturbing force of Venus, of a magnitude entirely unex- 

 pected. One depends upon the circumstance that eighteen times the mean 

 anomaly of Venus diminished by sixteen limes the mean anomaly of the 

 Earth increases at very nearly the same rale as the mean anomaly of the 

 Moon : its co-efficient is 27" and its period 273 years. The other depends 

 upon the circumstance, that eiglit limes the mean anomaly of Venus in- 

 creases at very nearly the same rate as thirteen times the mean anomaly of 

 the Earth : its co efficient is 23" and its period 239 years. The combina- 

 tion of these two explains almost perfectly the error of epoch, which had 

 so long been a subject of difficulty. The discovery of these two inequali- 

 ties, whether we regard the pecularlity of their laws, the labours expended 

 upon the investigations, or the perfect success of their results, must be 

 regarded as the most important step made in physical astronomy for many 

 years." 



Tides of the Air. — Tangible Astronomv. 



The doctrine of the influence of the moon and of the sun on the tides was 

 no sooner established than it became eminently probable that an inlluence 

 exerted so strongly upon a fluid so heavy as water could not but have the 

 lighter and all but imponderable fluid of air under its gra^p. I speak not 

 of the influence attributed to the moon in the popular language and belief 

 of nations ancient and modern, — of Western Europe and of Central Asia, iu 

 respect to disease ; but of the direct and measureable influence of the moon 



and of the sun in respect to the air. It is now clear, as the result of the 

 oliservations at St. Helena by my friend Col. Sabine, that as on the waters, 

 so on the atmosphere there is a corresponding influence exerted by the same 

 causes. There are tides in the air as in the sea ; the extent is of course 

 determinable only by the most careful observatious with the most delicate 

 instruments; since the minuteness of the effect, both in itself and in com- 

 parison with the disturbances which are occasioned in the equilibrium of 

 the atmosphere from other causes, must always present great difficulty in 

 the way of ascertaining the truth— and had, in fact, till Col. Sabine's re- 

 searclies, prevented any decisive testimony of the fact being obtained by 

 direct information. But the hourly observations of the barometer, made 

 for some years past at the Meteorological and Magnetical Observatory at 

 St Helena, have now placed beyond a doubt the existence of a lunar atmo- 

 spheric tide. It appears that in each day the barometer at St. Helena 

 stands, on an average, four thousandths of an inch higher at the two periods 

 when the moon is ou the meridian above or below ihe pole than when she 

 is six hours distant from the meridian on either side ; the progressioii be- 

 tween this maximum and minimum being moreover continuous and unin- 

 terrupted :— thus furnishing a new element in the attainment of physical 

 truth; and, to quote the expression of a distinguished foreigner now pre- 

 sent, which he uttered in my own house, when the subject was mentioned, 



" We are thus making astronomical oljservations with the barometer" 



that is, we are reasoning from the position of the mercury in a barometer, 

 which we can touch, as to the position of the heavenly bodies which, un- 

 seen by us, are induencing its visible fall and rise. " It is no exaggeratiou 



to say," — and here I use the words of my friend, the Rev. Dr. Robinson, 



"that we could even, if our satellite were incapable of reflecting light, 

 have determined its existence, nay, more, have approximated to its eccen- 

 tricity and period." 



Animal Electricity. 



In Physiology, the most remarkable of the discoveries, or rather im- 

 provements of previous discoveries, which the past year has seen, is, per- 

 haps, that connected with the labours of the distinguished Tuscan philoso- 

 pher, Matteucci. I refer in this instance to his experiments on the gene 

 ration of electric currents by muscular contraction iu the living body. This 

 subject he has continued to pursue; and, by the happy combination of the 

 rigorous methods of physical experiment with the ordinary course of phy- 

 siological research. Prof. Matteucci has fully established the iuiponaiit 

 fact of the existence of an electrical current — feeble, indeed, and such as 

 could only be made manifest by his own delicate galvanoscope— between 

 the deep and the superficial parts of a muscle. Such electric curivnts 

 pervade every muscle in every species of animal which has been the sub. 

 ject of experiment ; and may, therefore, be inferred to be a general pheno- 

 menon of living bodies. Even after life has been extinguished by violence, 

 these currents continue for a short time ; but they cease more speedily iu 

 the muscles of the warm-blooded than in those of the cold-blooded animals. 



The delicate experiments of Alatteucci on the torpedo agree with those 

 made by our own Faraday upon the Gyinnotus ekclricus, in proving that 

 the shocks communicated by those fishes are due to electric currents gene- 

 rated by peculiar electric organs, which owe their most immediate and 

 powerful stimulus to the action of the nerves. — In both species of fishes 

 the electricity generated by the action of their peculiar organised batteries 

 — besides its benumbing and stunning effects on living animals, — renders 

 the needle magnetic, decomposes chemical compounds, emits the spark, 

 and, in short, exercises all the other known powers of the ordinary electri- 

 city developed in inorganic matter or by the artificial apparatus of the la- 

 boratory. 



Etherization. 



This is the subject of the influence of the vapour of ether ou the hiimau 

 frame— a discovery of the last year, and one the value of which iu diminish- 

 ing human pain has been experienced iu countless instances, in every 

 variety of disease, and especially during the performance of trjing and 

 often agonizing operations. Several experimenis on the tracts and nerve 

 roots appropriated respectively to the functions of sensation and volition 

 have been resumed and repeated in connexion with this new agency on the 

 nervous system. Messrs. Flourens and Longet have shown that the sen- 

 sational functions are first affected, and are completely, though tempuraril*, 

 suspended under the operation of the vapour ot ether; then the mental oi 

 cerebral powers; and, finally, the motor and excito-motor forces are abro- 

 gated. It would seem that the stimulus of ether applied so largely or con- 

 tinuously -as to produce that effect is full of danger— and that weak consti- 

 tutions are sometimes unable to rally and recover from it ; but that when 

 the influence is allowed to extend no further thau to the suspension of sen- 

 sation, the recovery is as a general rule complete. 



MlCROSCOFlSM. 



In no department of the science of organized bodies has the progress 

 been greater or more assured than in that which relates to the microscopic 

 structure of the constituent tissues of animal bcdies, both in their healthy 

 and in their morbid slates; and this progress is specially marked in this 

 country during the period which has elapsed since the communication to 

 the British Association by Professor Owen of his researches info the inti- 

 mate structure of recent and fossil teeth. 



The result of these researches having demonstrated the constancy of well 

 defined and clearly appreciable characters in the dental tissues of each 

 species of animal, (by which characters such species could be determined. 



