141 S.E. 67); Scott v. Wimberly, 188 Ga. 148 ( 3 S.E.2d 71). Furthermore, no request was made; and in the absence of such, the omission to charge that circumstantial evidence alone might be sufficient to show insanity was not erroneous. See, in this connection, Cowart v. Strickland, 149 Ga. 397 (4) ( 100 S.E. 447, 7 A.L.R. 1110). It has been held many times that where a conviction depends solely on circumstantial evidence, the judge should, even without request, charge the rule on circumstantial evidence as stated in the Code, § 38-109; but that question is not involved in the instant case, and it is not so contended. The rule to be applied is that where the judge charges correctly the general principles applicable to the issues, if more specific instructions are desired they should be requested. Ford v. Ford, 146 Ga. 164 (3) ( 91 S.E. 42); Rountree v. Neely, 147 Ga. 435 ( 94 S.E. 542); Betts v. State, 157 Ga. 844, 846 ( 122 S.E. 551); Maner v. State, 181 Ga. 254 (5) ( 181 S.E. 856); Roberson v. State, 190 Ga. 661 (2), 662 ( 10 S.E.2d 173). We do not mean to say that the particular charge should have been given if it had been requested, for there may be other reasons why it was properly omitted.