June 15, 1876] 



NATURE 



161 



President, in a lecture delivered by him to the Biitiih Associa- 

 t:on at Bradford, that the solar heat, if fully exercised all over 

 the globe, supposing that globe to be entirely covered with 

 water, would be sufficient to evaporate a layer 14 feet deep of 

 water per annum. Now assuming 10 lbs. of water evaporated 

 from the temperature of the air into steam by the combustion of 

 I lb. of coal (a much larger result than unhappily is got in regular 

 work), this would represent an effect obtained from the sun's 

 rnys on each acre of water equal to the combustion of 1680 tons 

 of coals per annum, or to about 92 cwt. of coal per acre per 

 twenty-four hours ; or enough to maintain an engine of 200 gross 

 indicated horse-power day and night all the year round. When, 

 however, we consider the effect of the sun, not upon the surface 

 of water but upon the earth, and deal with its power of pro- 

 ducing beat-giving material, the result compares very unfavour- 

 ably with the work done by the sun itself ; and this, no doubt, 

 arises first, from the fact that the sun is frequently obscured, and 

 second, from the fact that a large portion of the energy of the 

 sun is spent in evaporating moisture from the ground, and not in 

 the direct production of combustible material. - I have found it 

 extremely diffi cult to obtain any reliable data as to the weight of 

 fuel grown per acre per annum. If we take the sugar cane, we 

 find that in extremely favourable cases as much megass and sugar 

 together are produced as would equal in calorific effect about five 

 tons of good Welsh coal. Coming to our own country and 

 dealing with a field of wheat, the wheat and straw together may 

 be taken as being equal probably to about two tons of coal as a 

 maximum. The statements made to me with regard to the 

 production of timber per acre per annum, when grown for the 

 purpose of burning, are very various ; but the best average I can 

 make from them is that in this country there is produced as much 

 wood as is equal in calorific effect to about i^ tons of good coal 

 per acre. Comparing these productions of heat-giving material 

 with the energy of the sun, as shown in the evaporation of water, 

 one shows how tempting a field is that of the direct employment 

 of the solar rays as a source of power ; more especially, when it 

 is remembered that those rays are obtained from week to week, 

 and ytar to year, without having to wait the tardy growth of the 

 fuel-destined tree. 



I will now ask you to consider with me the prime movers that 

 owe their energy to the heat developed by the combustion of 

 some ordinary kind of fuel — coal or wood. Passing by as a mere 

 toy and not an actual prime mover, the reactionary steam sphere, 

 the eoliopile of Hero, I will come at once to those simple forms 

 of heat-engine (whether worked by steam or the expansion of 

 air), by which water was to be raised. Solomon de Caus, in 

 his work of 161 5, already mentioned, says that if you fill a 

 globe with water and have in its upper part a pipe dipping 

 nearly to the bottom, and if you put the globe upon the fire the 

 heat will cause the expansion of the contents, and the water will 

 be delivered in a jet out of the tube. 



The Marquis of Worcester in his " Century of Inventions," 

 published in 1659, makes, as is well known, a similar proposition, 

 but it does not appear that these machines were seriously con- 

 templated for practical use. Papin (I take Belidor's Article 

 No. 1,276 as my authority) in 1698 {as appears in his pamphlet 

 of 1707) experimented by order of Charles the Landgrave of 

 Hessen Cassel with the view of ascertaining how to raise water 

 by the aid of fire. But his experiments were intemxpted and he 

 did not resume them until Leibnitz, by a letter of Jan. 6, 1705, 

 called his attention to what Savery was doing in England, send- 

 ing him a copy of a London print of a description of Savery's 

 engine. This engine, which of course is well known to you, is 

 illustrated by a model in this collection, and now on the table 

 before me. Savery employed a boiler, the steam from which was 

 admitted into a vessel furnished like the sun-pump of Belidcr 

 with a suction pipe and clack and a delivery pipe and clack ; the 

 steam being shut off', cold water was suffered to flow over the 

 vessel, a vacuum was made and water raised into the vessel, 

 which was expelled out of the delivery pipe upon the next ad- 

 mission of steam, the cocks being worked by hand. This machine 

 came into very considerable use and was undoubtedly the first 

 practical working steam-engine. It had, however, the defect of 

 consuming a large quantity of steam, as the steam not only came 

 into contact with the cold vessel but also with the surface of the 

 water in that vessel. Papin, as we know, obviated a portion of 

 this loss by the employment of a floating piston placed so as to 

 keep the steam from actual contact with the surface of the water. 

 We have in the collection. No. 2,007, a cylinder from Hessen 

 Cassel, said to be of the date of 1699 and to have been intended 



for employment in Papia's machine, but it is difficult to say for 

 what part of the apparatus it could have been designed, inasmuch 

 as the cylinder is provided with a flange at one end only and no 

 means, so far as I can ascertain, exist for closing the other end. 

 You will see from the diagram that which no doubt is already 

 well known to you; Papin did not propose to condense the steam, 

 and by its condensation to " draw up " the water (to use a fami- 

 liar expression) but intended that the vessel should be charged 

 by a supply from above, and, that the steam should be employed 

 only to press on the floating piston and to drive the water out. 

 Papin, however, hoped to use his engine, not merely as a water- 

 raiser, but as a fource of rotary power by allow-ng the water to 

 issue from the air vf srel, ro as to impinge upon the pallets of a 

 water-'wheel and thus produce the required revolution. 

 {To be continued.^ 



SCIENTIFIC SERIALS 



American Journal of Science and Aits, May. — Mr. Hold en 

 here collates various observations made en nebula M 17 (the 

 figure of which is like that of a Greek capital Omega) from 1833 

 to 1875. The drawings show that the western end has moved 

 relatively to its contained stars, and always in the same direction. 

 It may be a veritable change in the structure of the nebula itself 

 or the bodily shifting of the whole nebula in space. — Mr. Trow- 

 bridge states that the application of thin plates of soft iron on 

 the poles of two straight electro-magnets, wiih bundles of fine 

 iron wires for cores, increases the strength c f the spark at the 

 poles of two secordary coils surrounding the electro-magnets, 

 400 per cent. The length of the spark is increased 100 per cent, 

 (but this is only manifested by using Leyden-jars of large capacity 

 with the secondary circuit). Instead of distributing the fix e wire 

 of a Ruhmkorff" coil on a straight electromagnet, as at present, 

 it should be distributed equally on two straight electro-magnets 

 whose poles are provided with armatures of bundles of thin plates 

 of soft iron. — Mr. Wilson having applied infusorial earth to land 

 sown in wheat, afterwsrds treated some of the wheat straw with 

 nitric acid, and found that the siliceous remains consisted almost 

 wholly of the shields of diatomacese, the same as found in the 

 infusorial earth (only the larger discs, in their perfect form, being 

 absent). It would appear that simple or compound silicates are 

 useless as fertilising agents, and that silica can enter the plant 

 only in the free state. — In the first portion of a paper on the 

 sohd carbon compounds in meteorites, Mr. J. Laurence Smith, 

 after noting that in carbonaceous meteorites the mineral con- 

 stituents are mainly the same as in the so-called common type of 

 meteoric stones (viz., olivines, and pyroxenes, differing oiily in 

 the more or less compact form of these minerals), shows, that 

 even in the carbonaceous constituent they are strongly linked 

 even to the iron meteorites. — Mr. Fontaine continues his account 

 of the conglomerate series of West Virginia ; Mr. Dana describes 

 new forms of staurolite and pyrrholite ; and we also find chemical 

 notes on phosphorus oxychloride, and the oxydation product of 

 glycogen with bromine, silver oxide, and water. — A simple and 

 very accurate method of testing the unison of two forks is 

 (according to Mr. Spice) by holding them together over their 

 proper resonant column ; it the forks be very nearly in time, 

 beats will be perceived succeeding each other at long intervals, 

 or the sound will merely swell out again very slightly after it has 

 nearly died away. When the forks are absolutely alike, there 

 will be a gradual decrease of sound down to silence, without any 

 reinforcement at any time. 



The American Naturalist for May commences with an article 

 by the Rev. S. Lcckwood, on Animal Humour. Prof. Asa 

 Gray writes on Wild Gooseberries. Hon. J. D. Cox describes 

 multiplication by fission in Stentor mtilleri. An article on Primi- 

 tive man follows, after which Mr. A. S. Packard, jua, describes 

 and figures the Cave-beetles of Kentucky. Prof. Farlow writes 

 on University Instruction in Botany. General Notes and a few 

 short reviews follow, the number being completed by notes and 

 notices of meetings. 



Zeitschrift der Oesierreichischen Gesellschaft filr Meteorolo^ie, 

 March I. — This number contains a long article on the relations of 

 temperature and moisture in the lowest atmospheric strata during 

 the formation of dew, by Dr. R. Rubenson, of Stockholm. 

 Observations made by Dr. Hamberg, at Upsala, on temperature 

 at different heights on frosty nights led him to conclude that in 

 the lower strata temperature iccreases with height, and that the 



