The Wilhelm/Baynes translation of the I Ching is indeed beautiful and thorough. The names of the hexagrams are romanized using the Wade-Giles system, which was the standard method during Mr. Wilhelm's time. The Wade-Giles system was officially replaced by the Chinese Government in 1979 with the Pinyin system, for reasons having mostly to do with pronunciation. It can be confusing when trying to compare more recent translations with those such as the Wilhelm/Baynes translation (and others), since the names are romanized by the two different systems.

Below is a table showing the Pinyin and Wade-Giles versions of the names of each hexagram of the I Ching.
I Ching Hexagram Name Translations
     Pinyin   Wade-Giles (Wilhelm/Baynes)
 1.  Qian     Ch'ien, The Creative
 2.  Kun      K'un, The Receptive
 3.  Zhun     Chun, Difficulty at the Beginning
 4.  Meng     Mêng, Youthful Folly
 5.  Xu       Hsü, Waiting
 6.  Song     Sung, Conflict
 7.  Shi      Shih, The Army
 8.  Bi       Pi, Holding Together
 9.  Xiaoxu   Hsiao Ch'u, The Taming Power of the Small
10.  Lü       Lü, Treading
11.  Tai      T'ai, Peace
12.  Pi       P'i, Standstill
13.  Tongren  T'ung Jên, Fellowship with Men
14.  Dayou    Ta Yu, Possession in Great Measure
15.  Qian     Ch'ien, Modesty
16.  Yu       Yü, Enthusiasm
17.  Sui      Sui, Following
18.  Gu       Ku, Work on What Has Been Spoiled
19.  Lin      Lin, Approach
20.  Guan     Kuan, Contemplation
21.  Shike    Shih Ho, Biting Through
22.  Bi       Pi, Grace
23.  Bo       Po, Splitting Apart
24.  Fu       Fu, Return
25.  Wuwang   Wu Wang, Innocence
26.  Daxu     Ta Ch'u, The Taming Power of the Great
27.  Yi       I, The Corners of the Mouth
28.  Daguo    Ta Kuo, Preponderance of the Great
29.  Kan      K'an, The Abysmal
30.  Li       Li, The Clinging
31.  Xian     Hsien, Influence
32.  Heng     Hêng, Duration
33.  Dun      Tun, Retreat
34.  Dazhuang Ta Chuang, The Power of the Great
35.  Jin      Chin, Progress
36.  Mingyi   Ming I, Darkening of the Light
37.  Jiaren   Chia Jên, The Family
38.  Kui      K'uei, Opposition
39.  Jian     Chien, Obstruction
40.  Xie      Hsieh, Deliverance
41.  Sun      Sun, Decrease
42.  Yi       I, Increase
43.  Guai     Kuai, Break-through
44.  Gou      Kou, Coming to Meet
45.  Cui      Ts'ui, Gathering Together
46.  Sheng    Shêng, Pushing Upward
47.  Kun      K'un, Oppression
48.  Jing     Ching, The Well
49.  Ge       Ko, Revolution
50.  Ding     Ting, The Caldron
51.  Zhen     Chên, The Arousing
52.  Gen      Kên, Keeping Still
53.  Jian     Chien, Development
54.  Guimei   Kuei Mei, The Marrying Maiden
55.  Feng     Fêng, Abundance
56.  Lü       Lü, The Wanderer
57.  Xun      Sun, The Gentle
58.  Dui      Tui, The Joyous
59.  Huan     Huan, Dispersion
60.  Jie      Chieh, Limitation
61.  Zhongfu  Chung Fu, Inner Truth
62.  Xiaoguo  Hsiao Kuo, Preponderance of the Small
63.  Jiji     Chi Chi, After Completion
64.  Weiji    Wei Chi, Before Completion
The names of the trigrams in the two systems are less confusing, but are listed here for completeness.
I Ching Trigram Name Translations
     Pinyin   Wade-Giles (Wilhelm/Baynes)
 1.  Qian     Ch'ien
 2.  Kun      K'un
 3.  Zhen     Chên
 4.  Kan      K'an
 5.  Gen      Kên
 6.  Xun      Sun
 7.  Li       Li
 8.  Dui      Tui

The Pinyin versions of the trigram and hexagram names are taken from "The Zhou Book of Change" (Chinese-English Bilingual Edition), translated into English by Fu Huisheng, Shangdong Friendship Press, 2000.