3M Company COM 88579y101 23941 113622 SH SOLE 0 0 113622 A T & T Inc New COM 00206r102 364 10842 SH SOLE 0 0 10842 Abbott Labs COM 002824100 1061 14456 SH SOLE 0 0 14456 Abbvie Inc. Com COM 00287y109 1791 18933 SH SOLE 0 0 18933 Alphabet Inc Cap Sk Cl A COM 02079k305 507 420 SH SOLE 0 0 420 Amazon.Com Inc COM 023135106 1224 611 SH SOLE 0 0 611 Apergy Corp Com COM 03755l104 613 14077 SH SOLE 0 0 14077 Apple Computer COM 037833100 11961 52987 SH SOLE 0 0 52987 Auto Data Processing COM 053015103 32015 212496 SH SOLE 0 0 212496 Becton Dickinson COM 075887109 18810 72068 SH SOLE 0 0 72068 Bellicum Pharmaceutica COM 079481107 104 16900 SH SOLE 0 0 16900 Berkshire Hathaway Cl B COM 084670702 482 2252 SH SOLE 0 0 2252 Black Stone Minerals L Com Uni COM 09225m101 1293 70998 SH SOLE 0 0 70998 Bristol Myers Squibb COM 110122108 338 5450 SH SOLE 0 0 5450 CVS Health COM 126650100 11307 143634 SH SOLE 0 0 143634 Chevron Corp COM 166764100 2678 21902 SH SOLE 0 0 21902 Coca-Cola COM 191216100 18568 401996 SH SOLE 0 0 401996 Dominion Energy Inc COM 25746U109 751 10680 SH SOLE 0 0 10680 Donaldson COM 257651109 30813 528889 SH SOLE 0 0 528889 Dorchester Minerals LP COM 25820R105 1490 73023 SH SOLE 0 0 73023 Dover COM 260003108 19556 220896 SH SOLE 0 0 220896 Dow Dupont Inc Com COM 26078j100 354 5503 SH SOLE 0 0 5503 Ecolab COM 278865100 27355 174483 SH SOLE 0 0 174483 Emerson Electric COM 291011104 20805 271680 SH SOLE 0 0 271680 Exxon Mobil Corp COM 30231g102 4008 47139 SH SOLE 0 0 47139 FedEx COM 31428x106 26500 110056 SH SOLE 0 0 110056 First Financial Bankshares COM 32020R109 217 3668 SH SOLE 0 0 3668 Home Depot Inc COM 437076102 340 1643 SH SOLE 0 0 1643 Honeywell International COM 438516106 21007 126243 SH SOLE 0 0 126243 Illinois Tool Works COM 452308109 27779 196849 SH SOLE 0 0 196849 Intel COM 458140100 25734 544173 SH SOLE 0 0 544173 International Business Machine COM 459200101 528 3494 SH SOLE 0 0 3494 Intuitive Surgical Inc Com New COM 46120E602 560 975 SH SOLE 0 0 975 Johnson & Johnson Com COM 478160104 24803 179511 SH SOLE 0 0 179511 Lowes Cos Inc COM 548661107 364 3166 SH SOLE 0 0 3166 Luminex Corp COM 55027E102 1075 35453 SH SOLE 0 0 35453 Magellan Midstream Prt Unit Rp COM 559080106 474 7000 SH SOLE 0 0 7000 Mastercard Inc Cl A COM 57636q104 255 1147 SH SOLE 0 0 1147 McCormick COM 579780206 14993 113799 SH SOLE 0 0 113799 McDermott Intl Inc COM 580037109 440 23863 SH SOLE 0 0 23863 Medtronic PLC COM g5960l103 649 6593 SH SOLE 0 0 6593 Microsoft COM 594918104 44250 386906 SH SOLE 0 0 386906 National Instr COM 636518102 22765 471022 SH SOLE 0 0 471022 Netflix Inc COM 64110L106 251 670 SH SOLE 0 0 670 Nokia COM 654902204 85 15250 SH SOLE 0 0 15250 Nordson COM 655663102 36508 262834 SH SOLE 0 0 262834 Novartis AG COM 66987V109 17043 197807 SH SOLE 0 0 197807 Paccar COM 693718108 17350 254435 SH SOLE 0 0 254435 PepsiCo COM 713448108 19544 174811 SH SOLE 0 0 174811 Pfizer, Inc. COM 717081103 779 17674 SH SOLE 0 0 17674 Phillips 66 COM COM 718546104 343 3042 SH SOLE 0 0 3042 Procter & Gamble COM 742718109 17907 215150 SH SOLE 0 0 215150 Regeneron Pharmaceuticals Inc COM 75886F107 404 1000 SH SOLE 0 0 1000 Sabine Royalty Trust UBI COM 785688102 591 14000 SH SOLE 0 0 14000 San Juan Basin Royalty Trust COM 798241105 3211 647452 SH SOLE 0 0 647452 Schlumberger Ltd COM 806857108 11703 192099 SH SOLE 0 0 192099 Sysco Corp COM 871829107 350 4774 SH SOLE 0 0 4774 Taiwan Semiconductor COM 874039100 2754 62362 SH SOLE 0 0 62362 Telefonica de Espana COM 879382208 222 28192 SH SOLE 0 0 28192 United Parcel Svc Cl B COM 911312106 17916 153456 SH SOLE 0 0 153456 Verizon Communications COM 92343v104 223 4168 SH SOLE 0 0 4168 Walt Disney COM 254687106 232 1983 SH SOLE 0 0 1983 Waste Management Inc Del COM 94106L109 316 3500 SH SOLE 0 0 3500