424 



NA TURE 



[March i, 1900 



OUR ASTRONOMICAL COLUMA. 



.•VSTRONOMICAI. OCCURRENCES IN MARCH. 

 March 2. 6h. Mercury in conjunction with moon. Mercury 

 4° 37' S. _^ , 



7. 23h. Mercury at greatest elongation east (18 16). 



8. 6h. 13m. to 7h. 3m. Neptune occulted by the moon. 

 8. gh. 31m. Minimum of Algol ()8 Persei). 



10. I3h. 43m. to I4h. 40m. Occultation of/Geminorum 

 (mag. 5 '2) by the moon. 



10. I4h. i8m. to I5h. 57m. Transit of Jupiter's Sat. 



III. 



11. I4h. 13m. to I5h. 6m. Occultation of 29 Cancri 



(mag. 5*9) by the moon. 

 15. Venus. Illuminated portion of disc, 0708. Mars, 



0993. 

 45. I5h. 20m. to i6h. 25m. Occultation oi e Leonis 



(mag. 5'i) by the moon. 

 17. i8h. 7m. Transit (egress) of Jupiter's Sat. III. 

 21. I7h. 19m. to I7h. 33m. Occultation of pOphiuchi 



(mag. 5"3) by the moon. 

 23. 20h. Saturn in conjunction with the moon. 

 23. 20h. 35m. to 2ih. 46m. Occultation of Saturn by 



the moon. 

 28. iih. 12m. Minimum of Algol ()3 Persei). 

 31. 8h. im. Minimum of Algol (j8 Persei). 



Comet Giacobini (1900a).— The Astronomische Nachrichten 

 (Bd. 151, No. 3624) contains an ephemeris and the elements 

 of this comet computed from the observations made on 

 January 31, February 3 and 6, at the Nice Observatory, by 

 M. Giacobini. 



Elements. 

 T=I900 April 28"2o85 Paris Mean Time. 



(Bd. 151, No. 3623) Dr. Karl Kostersitz describes the photo- 

 graphic equipment which he employed at the Vienna Observa- 

 tory for the detection of the Leonid and Bielid meteors in 

 November 1899. A plate accompanies the article, showing the 

 method of mounting the cameras, four of which were used with- 

 out driving apparatus. The cameras were all fitted with rapid 

 portrait lenses, and great care was taken to accurately orient 

 the plates for subsequent reduction. 



MOTIVE POWER. STEAM TURBINES. HIGH 

 SPEED NAVIGATION.^ 



*nPWENTY centuries ago the political power of Greece was 

 ^ broken, although Grecian civilisation had risen to its 

 zenith. Rome was growing continually stronger, and was 

 rapidly gaining territory by absorbing weaker States. Egypt, 

 older in civilisation than either Greece or Rome, fell, but two 

 •centuries later, before the assault of the younger States, and 

 became a Roman province. Her principal city at this time was 

 Alexandria, a great and prosperous city, the centre of the 

 commerce of the world, the home of students and of learned 

 men, its population the wealthiest and most civilised of the then 

 known world. 



It is among the relics of that ancient Egyptian civilisation 

 that we find the first records of the early history of the steam- 

 engine. In Alexandria, the home of Euclid, and possibly 

 contemporary with Archimedes, Hero wrote his " Spiritalia seu 



tution on January 26, by the 



i A Discourse delivered at the Royal It 

 Hon, C. A. Parsons, F.R.S. 



NO. I ^^-^^ VOL. 6l] 



Pneumatica." It is doubtful if Hero was the inventor of the 

 contrivances and apparatus described in his work ; it is more 

 probable that they were devices generally known at the time. 

 Nothing in the text, however, indicates to whom the several 

 machines are to be ascribed. Two of these machines are of 

 special interest. The first utilised the expansive force of air in 

 a closed vessel heated externally, the pneumatic force being 

 applied to the surface of water in other vessels, and the hydraulic 

 force utilised for opening the doors of a Grecian temple, and 

 working other pseudo-magic contrivances. 



Then after describing several forms of cylindrical boilers, and 

 the use of the steam jet for accelerating combustion, he comes to 

 the first of a type of steam engine, the steam turbine, which is 

 the subject of our discourse this evening. 



This is a veritable steam engine. The cauldron contains 

 water, and is covered by a steam-tight cover, a globe is sup- 

 ported above the cauldron by a pair of tubes, one terminating 

 in a pivot, and the other opening directly through the trunnion 

 joint into the sphere ; short bent pipes are attached to dia- 

 metrically opposite points on the equator. The steam generated 

 in the cauldron passes up into the sphere and issues tangen- 

 tically from the bent pipes, and by the reaction causes the sphere 

 to rotate. 



It seems uncertain whether this machine was ever more than 

 a toy, or whether it was used by the Greek priests for producing 

 motion of apparatus in their temples ; but from our experience 

 within the last twenty years it appears that, with some improve- 

 ments in design and construction, it could have been applied to 

 perform useful work at the date of Hero, and further that, 

 when so improved, it might have claimed a place among 

 economical steam engines, even up to the middle of the present 

 century. 



A few years ago I had an engine constructed to test the 

 capabilities of this class of reaction steam turbine, the only 

 difference between this engine and Hero's being that the 

 sphere was abolished, as a useless incumbrance, the arms 

 were made of thin steel tube of oval form, so as to offer the 

 least resistance to their motion, and the whole was enclosed in a 

 cast iron case which was connected to a condenser. When sup- 

 plied with steam at a pressure of 100 lbs. per square inch, and a 

 vacuum in the case of 27" of mercury, a speed of 5000 revolu- 

 tions per minute was attained, and an effective power was 

 realised of 20 horse, and the consumption of steam was only 

 40 lbs. per brake horse-power. By this very creditable per- 

 formance, I was encouraged to further test the system, and con- 

 structed a compound reaction engine, in which the steam was 

 caused to pass successfully through three pairs of arms on one 

 hollow shaft, each pair being contained in a separate compart- 

 ment through which the shaft passed, suitable metallic packing 

 preventing the passage of steam from one compartment to the 

 next. The performance of this engine was, however, not 

 superior to that of the single two-arm Hero's engine, for the 

 simple reason that the excessive resistance to motion of the 

 arms in the denser steam of the compartments more than neu- 

 tralised the gain from the compound form. The performance 

 of this engine was, however, sufficiently good to have it placed 

 on a par with many ordinary steam engines in the middle of the 

 present century. 



The great barrier to the introduction of Hero's engine was 

 undoubtedly the excessive speed of revolution necessary to ob- 

 tain economical results, and with the crude state of mechanical 

 engineering at that time, it would have been a matter of some 

 difficulty to construct the turbine engine with sufficient 

 accuracy of workmanship for satisfactory results, to say nothing 

 of the necessary gearing for applying the power to ordinary 

 useful purposes. 



The next steam engine mentioned in history, which is capable 

 of practical and useful development, is Bianca's in 1629. It is 

 of the simplest form, a jet of steam from a steam boiler im- 

 pinges on a paddle-wheel and blows it round. This form of 

 engine has > since 1889 been developed by Dr. De Laval, of 

 Stockholm, with great ingenuity, and is extensively used for 

 moderate powers on the Continent. The speed is, however, 

 necessarily very high in order to obtain economy in steam, and 

 spiral reduction gearing is used in order that the speed of revo- 

 lution may be reduced for the application of the power. The 

 improvements that have been made in Bianca's steam turbine 

 by De Laval are firstly, the ordinary steam jet is replaced by a 

 diverging conical jet, which permits of the expansion of the 

 steam before it emerges from the jet, and so transforming the 



