Apocalypse Explained # 501
501. Verse 7. And the first angel sounded, and there was hail and fire mingled with blood; and they were cast unto the earth; and the third part of the trees was burnt up, and all green grass was burnt up.
7. "And the first angel sounded," signifies influx out of heaven, and in consequence the first change n. 502; "and there was hail and fire mingled with blood," signifies the destroying infernal falsity and evil, mingled with the truths and goods of the Word, to which violence was offered (n. 503, 504); "and they were cast unto the earth," signifies progression towards the lower parts (n. 505); "and the third part of the trees was burnt up," signifies that the perceptions and knowledges of truth and good were destroyed by cupidities arising from evil loves n. 506; "and all green grass was burnt up," signifies that all true knowledge [scientificum] was destroyed by the cupidities of the same loves n. 507.
Apocalypse Explained # 262
262. As of a trumpet speaking with me, signifies clear and manifest. This is evident from the signification of "trumpet," as being Divine truth manifested and revealed out of heaven (of which above, n. 55. A voice that is heard out of heaven with those who are in the spirit is heard usually as a human voice; but it was heard "as a trumpet speaking" because it was clearly and manifestly perceived by the angels, and what is clearly and manifestly perceived by them falls loudly into the hearing of the spirit; and this was done with John that his attention might be awakened, and thence his sight, lest anything should be obscure to him. This is meant by "the voice of a trumpet" in other places also (Matthew 24:31; Zechariah 9:14; Psalms 47:5; Revelation 8:2, 7-8, 13; 9:1, 13-14; 10:7; 18:22).