Dr. Guest treats sounds as having in themselves the suggestion of more or less definite ideas, this suggestiveness being explainable by physical causes. Thus the trembling character of _l_ suggests trepidation, as in "Double, double, toil and trouble." _R_ suggests harsh, grating, or rattling noises; the sibilants are appropriate to the expression of shrieks, screams, and the like; _b_ and _p_, because of the compression of the lips, suggest muscular effort; _st_, from a sudden stopping of the _s_, suggests fear or surprise; _f_ and _h_ also fear, because of their whispering quality. Hollow sounds (_au_, _ow_, _o_, and the like) suggest depth and fulness. Guest quotes in this connection an interesting passage from Bacon's _Natural History_ (ii. 200): "There is found a similitude between the sound that is made by inanimate bodies, or by animate bodies that have no voice articulate, and divers letters of articulate voices; and commonly men have given such names to those sounds as do allude unto the articulate letters; as trembling of hot water hath resemblance unto the letter _l_; quenching of hot metals with the letter _z_; snarling of dogs with the letter _r_; the noise of screech-owls with the letter _sh_; voice of cats with the diphthong _eu_; voice of cuckoos with the diphthong _ou_; sounds of strings with the diphthong _ng_. A. W. Schlegel went even farther in suggesting a subtle symbolism in sounds apart from descriptive qualities. Thus he regarded _a_ as suggestive of bright red, and as symbolizing youth, joy, or brightness (as in the words _Strahl_, _Klang_, _Glans_); _i_ as suggestive of sky-blue, symbolic of intimacy or love; and so with other vowel sounds. (See Ehrenfeld's monograph, p. 57.) In general it may be said that it is dangerous to attempt to explain the special effects of tone-color in verse, except where it is obviously descriptive, the appreciation of such effects being a subtle and a more or less individual matter. On this subject Mr. Gurney makes some interesting observations, in the essays cited above. He believes that the pleasurable effect of the sound-qualities in verse can never be dissociated from the sense of the words; that the most melodious verse cannot be appreciated if in a foreign language, unless read with particular expressiveness; and that the pleasure derived from what we roughly call melodious or harmonious verses is always due to the mystical combination of the appropriate sound with the poetic content. Dr. Johnson ridiculed the idea of tone-color, as appearing in Pope's teaching that the sound should be "an echo to the sense." See his _Life of Pope_, and especially the _Idler_ for June 9, 1759, in which he describes Minim the critic as reading "all our poets with particular attention to this delicacy of versification." Such a critic discovers wonders in these lines from _Hudibras_: