SPEAKING TRUMPET. 



SPECIFIC GRAVITY. 



691 



hollow oval box, divided into two portions, attached by a hinge so as 

 to resemble jaws, and by opening and closing them the sounds which 

 issued from a tube connected with the reed produced A, o, ou, and an 

 imperfect E, but not i. He afterwards succeeded in obtaining, from 

 different jaws, the sound of the consonants p, M, I. ; and by means of 

 these vowels and consonants he could produce such words as mamma, 

 papa, aula, lama, mulo. He afterwards succeeded in imitating the 

 human organs of speech by having only one mouth and one glottis. 

 The mouth consisted of a funnel- or bell-shaped piece of elastic gum, 

 to which was added a nose made of two tin tubes. When both tubes 

 were open, and the mouthpiece closed, a perfect M was produced ; and 

 when one was closed and the other open, an !f was sounded. He also 

 obtained a tolerable resemblance of the four sounds D, Q, K, T, or rather 

 a modified p, and at length succeeded in producing entire words and 

 sentences, such as Constantinopolit ; opera ; attronomy ; Vous ctes man 

 ami ; Je vovs aime de lout man aeur. We learn from a letter from 

 Mr. Thos. Collinson to Dr. Hutton, who had seen the machine in 

 London, and afterwards at Kempelen's house in Vienna, that the 

 sounds issued, not from a speaking figure, but from a rectangular box 

 about three feet long, placed upon a table and covered with a cloth. 

 Kempelen set it in action by introducing his hands beneath the cloth. 



Professor Willis, in the third volume of the ' Transactions of the 

 Cambridge Philosophical Society,' shows that by using a shallower 

 cavity than that employed by Kempelen, he could dispense with the 

 introduction of the hand, and by sliding a flat board over the mouth of 

 the cavity could obtain the whole series of vowels, in the order u, o, A, 

 , I. The apparatus was, of course, connected with a wind-chest and a 

 double pair of bellows. Mr. Willis also used cylindrical tubes containing 

 a reed, with a contrivance for varying the length of the tubes by means 

 of sliding joints. When the tube was much less than the length of a 

 stop-pipe in unison with the reed it sounded I : and by increasing the 

 length of the tube it gave E, A, o, and u ; but what was remarkable, 

 when the tube was lengthened so as to be 14 times the length of a 

 stop-pipe in unison with the reed, the vowels began to be sounded in 

 an inverted order, namely, u, o, A, E, and then again in a direct 

 order, i, E, A, o, u, when the length of the tube was equal with twice 

 that of a stop-pipe in unison with the reed. When the pitch of the 

 reed was very high, it was impossible to sound some of the vowels, 

 which Mr. Willis remarks is exactly the case with the human voice, 

 female singers being unable to pronounce u and o on the highest notes 

 of their voices. 



S 1'EAKING TRUMPET. The efficiency of this instrument is due 

 to the repeated reflection of the sound from side to side in passing 

 through it, and its ultimate reflection from the mouth of the trumpet, 

 in such a way aa either to collect the rays of sound into a focus at a 

 distance, or to project them forward in parallel lines, instead of allow- 

 ing them to diverge in all directions, fig. 1, illustrates this theory, 



Fig. 1. 



of which there are many modifications, some of them founded on the 

 supposition of a very close analogy between the motion of sound and 

 that of light. These have given rise to many suggestions respecting 

 the best form and degree of curvature of the sides of the trumpet. 

 Some writers recommend a simple cone, the mouth-piece being at the 

 apex : these explain the motion of the rays of sound on the principle 

 Bhown in Jig. 2, in which, aa in Jig. 1, the dotted lines represent the rays. 



Fig. 2. 



In Dr. Young's ' Lectures on Natural Philosophy,' the following 

 remarks occur : " If an ellipsis be prolonged without limit, it will 

 become a parabola ; hence a parabola is the proper form of the section 

 of a tube calculated for collecting a sound which proceeds from a great 

 distance into a single point, or for carrying a sound nearly in parallel 

 directions to a very distant place. It appears, therefore, that a para- 

 bolic conoid is the best form for a hearing trumpet, and for a speaking 

 trumpet ; but for both purposes the parabola ought to be much 

 elongated, and to consist of a portion of the conoid remote from the 

 vertex ; for it is requisite in order to avoid confusion, that the sound 

 should enter the ear in directions confined within certain limits : the 

 voice proceeds also from the mouth without any very considerable 

 divergence, so that the parts of the curve behind the focus would in 

 both cases be wholly useless. A trumpet of such a shape does not 

 very materially differ from a part of a cone, and conical instruments 

 are found to answer sufficiently well for practice ; it appears, however, 



unnecessary to suppose, as M. Lambert has done, that they differ essen" 

 tially in principle from parabolic trumpets. It is not yet perfectly 

 decided whether or no a speaking trumpet has any immediate effect in 

 strengthening the voice independently of the reflection of sound." 

 [EAR TECMPET.] 



Speaking Tubes are used in large buildings for conveying messages 

 from one part to another, and sometimes on shipboard from the cap- 

 tain's cabin to the topmast. These tubes are cylindrical, and the rays 

 of sound proceeding from the mouth at one end of the tube instead of 

 diverging in the air are confined within the tube, and successively 

 reflected from its sides, so that a much larger number of rays meet the 

 ear at the farther end than if they had travelled without being re- 

 flected. The shafts of mines, wells, and chimneys produce a similar 

 effect. 



SPECIAL OCCUPANCY. [OCCUPANCY.] 



SPECIALTY, SPECIALTY DEBT, or debt by special contract, 

 is a debt which becomes due or is acknowledged to be due by au 

 instrument under seal. [DEED.] 



The nature of a debt by simple contract is explained under SIMLPE 

 CONTRACT. 



Blackstone considers a debt of record, that is, a debt which appears 

 to be due by the judgment of a court <of record, as a " contract of the 

 highest nature, being established by the sentence of a court of 

 judicature." This is, however, an erroneous view of the matter. It is 

 simply a rule of law that a debt for which the judgment of a court of 

 record has been obtained has a priority over other debts. 



SPECIES. This word is used in mathematics, or rather has been 

 used, in two different senses. In the first place, by Euclid, who means 

 by figures of the same species those which have the same form, what- 

 ever may be their size. Thus, in the Data, when the form of a figure 

 is given, he designates it as given in species (T$ efSti ScSofufmv). The 

 word species is here used in its primitive sense of appearance. 



But the term was again used by Vieta in its logical sense, as opposed 

 to individual, in designating the algebraical notation which he first 

 distinctly proposed. Lawyers were in the habit of describing general 

 cases by using an individual name, as Caius or Julius, to signify any 

 person concerned, which they termed description by species. Vieta 

 borrowed the word to signify the use of letters to stand for numbers, 

 when such letters were used to designate members generally, without 

 reference to any one in particular. The logistics (a common term for 

 the science of calculation) thus introduced he called specious, and his 

 first tract on the simple operations of algebra is headed ' De Logistic^ 

 Speciosa.' Hence, for some time, the language of algebra was called 

 the specious notation. 



SPECIFIC ELECTRIC INDUCTION. [ELECTRICITY.] 



SPECIFIC GRAVITY, or, more properly, specific weir/Jtt, is a term 

 used to express the weight of any gas, liquid, or solid, under some 

 given volume ; but the unit of weight and unit of volume are usually 

 such, that for some one particular substance the weight of the unit of 

 volume shall be expressed by the unit of weight, or by 10 times, 100 

 times, or 1000 times that unit. Thus the numbers expressing the 

 specific gravities of different substances denote the actual weights of 

 those substances under the unit of volume; and hence the ratio 

 between the numbers expressing the specific gravities of any two 

 substances is the same as the ratio between the weights of those 

 substances under any two equal volumes, the density of the atmo- 

 sphere and also the states of those substances with respect to tempera- 

 ture being the same. 



Distilled water is the substance usually employed for the purpose of 

 comparing together the weights of all substances except the gases ; and 

 because the volume of any substance varies with its temperature, in 

 determining from experiment the specific gravity of any substance, the 

 weight under a given volume is reduced to that which it would 

 become at one constant temperature. The constant temperature 

 adopted in this country is, in general, that which is expressed by 60 

 of Fahrenheit's thermometer. 



From the experiments of Sir George Shuckburgh Evelyn it was 

 found that at the temperature expressed by 39 Fahr., the height of 

 the column of mercury in the barometer being 2978 inches, the 

 weight of a cubic foot of distilled water was 999'8066 ounces avoir- 

 dupois ; and reducing this weight conformably to the table of the 

 densities of water at different temperatures which had been given by 

 Biot, it will be found that at a temperature expressed by 60 Fahr., 

 and when the height of the mercurial column is 30 inches, the weight ' 

 of the cubic foot of water is 999'54 ounces. But in the Parliamentary 

 regulations, which were made in 1825, a cubic inch of water is stated 

 to weigh 252'456 troy grains, the temperature being 62 Fahr., and the 

 height of the barometrical column, 30 inches ; and 7000 troy grains 

 are made equivalent to one pound avoirdupois : hence it follows that 

 a cubic foot of water should weigh 997'1 36 ounces. Either of theso 

 numbers is sufficiently near 1000 to make it very proper that this last 

 should be adopted for the specific gravity of water, since a change in 

 the value of the avoirdupois ounce, which would be scarcely appre- 

 ciable in the ordinary transactions of commerce, would render the 

 ounce an accurate and convenient unit of weight, while the cubic foot 

 constitutes the unit of volume. 



In France, since the employment of the decimal scale of weights 

 and measures has become general, the cubic centimetre ('061028 cubic 



