January 29, 1892.] 



SCIENCE. 



65 



Airy began those great improvements in tlie methods of cal- 

 culating and publishing the astronomical observations made, 

 which have lud other observatories to take copy after him. 

 Airy was a methodical man, a professional and a business 

 man. He made his work conform to a scheme laid out the 

 year before, and that plan was strictly followed. His work 

 as an astronomer and a calculator is valuable, because it is 

 unbroken and comparable. The astronomical instruments 

 that have so long stood within the walls of Cambridge Ob- 

 servatory were made after his own plans and under his own 

 directions. 



In 1835 Professor Airy, then in his thirty-fourth year, was 

 appointed Astronomer Royal. For forty six years he filled 

 that position with marked^ ability. Under his master- 

 mind it is needless to say that the astronomical observatory 

 at Greenwich was completely changed. He placed the man- 

 ner of reducing the observations upon a more satisfactory 

 basis, and equipped the observatory with instruments of a 

 higher order of precision. In the year 1850, under his guid- 

 ance, a new meridian circle was erected. It has an object 

 glass of eight inches aperture and eleven feet six inches focal 

 length. In 1855, at his earnest solicitation, a large equa- 

 torial telescope was placed in the observatory. 



Professor Airj' was a man that not only combined the 

 philosopher with the mathematician, but was one that had an 

 inventive mind as well. This may be seen in the many 

 forms of astronomical instruments and their accessories due 

 to his very active brain. The value of the observations made 

 by him during his occupancy of the position of Astronomer 

 Royal at Greenwich, rests not only upon their accuracy and 

 dispatch in being published, but on their continuity. This 

 may be seen in his reduction of lunar observations from 1750 

 down to a late date, a most valuable series of observations. 



Airy was a man in whom his government had the utmost 

 confidence when it came to deciding questions of grave im- 

 port. He was the chairman of the royal commission em- 

 powered to supervise the delicate process of contriving new 

 standards of length and weight, the old standards having 

 been destroyed in the burning of the House of Parliament in 

 1834. He was called in consultation soon afterwards in re- 

 spect to removing the disturbance of the magnetic compass 

 in iron-built ships. He thereupon contrived a mechanical 

 combination which has been universally adopted. His re- 

 searches on the density of the earth, his fixing the breadth 

 of railways, his care in the equipment of the British expedi- 

 tion to observe the transit of Venus, and the reduction of the 

 observations after having been made, — all voice the great 

 confidence placed in him by his countrymen, and his worth 

 as a practical astronomer. 



The writings of Sir George Airy cover a great deal in the 

 field of philosophical and mathematical thought, and are 

 thorough in their discussion of each subject. His pen was 

 ever busy, and one has but to turn to the volumes of the 

 Cambridge Transactions, the Memoirs of the Royal Astro- 

 nomical Society, to the Philosophical Magazine, and the 

 Athenaeum, to find its fruits. But in the volumes issued 

 from the Greenwich Observatory we find the great life-work' 

 of Sir George Airy. They are the polished stones, the finely 

 carved pillars that have been used in building up the as- 

 tronomy of the nineteenth century. His principal works, 

 which have become books of reference, are: " Gravitation," 

 "Ipswich Lectures on Astronomy,'" "Errors in Observa- 

 tions," "Figure of the Earth," "Tides and Waves," 

 " Sound," and " Magnetism." 



On,e whose reputation as a man of such scientific attain- 



ment as Sir George Airy has deservedly received recogni- 

 tion, both from his own country and abroad. He has re- 

 ceived the Lelande gold medal of the French Institute in 

 honor of his important discoveries in astronomy. For his 

 successful optical theories he was awarded the Copley gold 

 medal of the Royal Society. The royal gold medal of the 

 same society has been given him in return for his tidal investi- 

 gations. Twice the gold medal of the Royal Astronomical 

 Society has been given him — first, in return for his discov- 

 ery of an inequality of long period in the movements of 

 Venus and the earth; second, to reward him for his reduc- 

 tion of the planetary observations. He has been enrolled 

 among the most honored members of . the Royal Astronomi- 

 cal Society, of the Cambridge Philosophical Society, and of 

 the Institute of Civil Engineers. For many years he has 

 been among the foreign correspondents of the Institute of 

 France, and other scientific societies on the continent. He 

 has secured the honorary degree of D.C.L. and LL D. from 

 each of the great universities of Great Britain — Edinburgh, 

 Oxford, and Cambridge. In May, 1872, he was gazetted a 

 Knight of the Batli. 



When the years shall have passed into centuries, and 

 coming astronomers are searching the records for valuable 

 data to be used in the discussion of questions in astronomy, 

 the observations and results determined by Sir George Bid- 

 dell Airy will be found of the highest value. 



Geo. a. Hill. 



STRUCTURE OF THE TRACHEA OF INSECTS.' 



Me. Lachlan's article on insects in- the " Encyc]opa3dia 

 Britannica" reproduces Blanchard's error of a double chi- 

 tinous wall for the tracheae with a spiral thread between. 

 Blanchard and Louis Agassiz superadded a peritracheal cir- 

 culation of blood. Joly's refutation of this view, in 1850, 

 failed to give the real cause of the error: this was 

 not, as suggested by him, due to bad injecting; but 

 it resulted from observing insects when moulting. At time 

 of moulting the trachea contains the old chitinous wall, dark 

 and enclosing air, and surrounded with exuding fluid be- 

 tween it and the new chitinous wall ; thus the appearance of 

 things is much as described by Blancbard, who mistook the 

 exuded fluid for circulating blood, and also mistook a tem- 

 porary state of matters for the normal state. 



The view published by me in the American Naturalist, 

 in 1884, that the spiral thickenings of the trachea are really 

 crenulations, channel-like transverse folds open outwards 

 (i.e., away from the lumen of the trachea) by a slit or As- 

 sure, was supported by indirect evidence, and needs to be 

 enforced so as to leave no doubt. Miall and Denny, in their 

 monograph on the cockroach, write as if they had been able 

 to unroll the spiral like that of a vegetable trachea, with- 

 out tearing the connecting membrane, and copy Chun's 

 very inaccurate figure, which ascribes a free continuous 

 spiral thread to the trachea of insects just as we find it in 

 the plants. 



A re-examination of the case brings out the singular result 

 that the whole machinery can be distinctly seen by the mi- 

 croscope to be such as I have described it. The profile of a 

 medium-sized trachea of any insect can be easily seen to be 

 grooved like the edge of a screw : all the more clearly if the 

 trachea is slightly stretched under the cover-glass. In the 

 living insect we may observe that the resiliency of the trans- 

 versely chanelled walls responds to the muscular contraction 



' Abstract of a paper read by G. Macloskie before the American Associa- 

 tion of Naturalists, Dec, 1891. 



