The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number: 3235-0006
Estimated average burden
hours per response: 23.8
COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
3M Company COM 88579y101 19,677 113,520 SH   SOLE   0 0 113,520
A T & T Inc New COM 00206r102 243 7,265 SH   SOLE   0 0 7,265
Abbott Labs COM 002824100 1,214 14,432 SH   SOLE   0 0 14,432
Abbvie Inc. Com COM 00287y109 1,093 15,028 SH   SOLE   0 0 15,028
Alcon Inc COM H01301128 4,118 66,369 SH   SOLE   0 0 66,369
Alphabet Inc Cap Sk Cl A COM 02079k305 474 438 SH   SOLE   0 0 438
Amazon.Com Inc COM 023135106 2,333 1,232 SH   SOLE   0 0 1,232
Apple Computer COM 037833100 12,156 61,417 SH   SOLE   0 0 61,417
Auto Data Processing COM 053015103 34,635 209,493 SH   SOLE   0 0 209,493
Becton Dickinson COM 075887109 18,312 72,662 SH   SOLE   0 0 72,662
Bellicum Pharmaceutica COM 079481107 24 13,900 SH   SOLE   0 0 13,900
Berkshire Hathaway Cl B COM 084670702 475 2,227 SH   SOLE   0 0 2,227
Black Stone Minerals L Com Uni COM 09225m101 1,100 70,998 SH   SOLE   0 0 70,998
Boeing Co. COM 097023105 380 1,043 SH   SOLE   0 0 1,043
CVS Health COM 126650100 8,178 150,086 SH   SOLE   0 0 150,086
Chevron Corp COM 166764100 2,735 21,978 SH   SOLE   0 0 21,978
Coca-Cola COM 191216100 20,307 398,802 SH   SOLE   0 0 398,802
ConocoPhillips COM 20825C104 443 7,256 SH   SOLE   0 0 7,256
Donaldson COM 257651109 26,546 521,941 SH   SOLE   0 0 521,941
Dorchester Minerals LP COM 25820R105 971 53,023 SH   SOLE   0 0 53,023
Dover COM 260003108 21,943 218,989 SH   SOLE   0 0 218,989
Ecolab COM 278865100 34,046 172,438 SH   SOLE   0 0 172,438
Emerson Electric COM 291011104 17,912 268,462 SH   SOLE   0 0 268,462
Exxon Mobil Corp COM 30231g102 3,102 40,475 SH   SOLE   0 0 40,475
Facebook Inc Cl A COM 30303m102 254 1,318 SH   SOLE   0 0 1,318
FedEx COM 31428x106 18,151 110,549 SH   SOLE   0 0 110,549
First Financial Bankshares COM 32020R109 226 7,336 SH   SOLE   0 0 7,336
Home Depot Inc COM 437076102 452 2,173 SH   SOLE   0 0 2,173
Honeywell International COM 438516106 21,844 125,117 SH   SOLE   0 0 125,117
Illinois Tool Works COM 452308109 29,446 195,249 SH   SOLE   0 0 195,249
Intel COM 458140100 25,883 540,697 SH   SOLE   0 0 540,697
International Business Machine COM 459200101 436 3,162 SH   SOLE   0 0 3,162
Intuitive Surgical Inc Com New COM 46120E602 1,141 2,175 SH   SOLE   0 0 2,175
J.P. Morgan Chase & Co. COM 46625H100 232 2,073 SH   SOLE   0 0 2,073
Johnson & Johnson Com COM 478160104 24,652 176,995 SH   SOLE   0 0 176,995
Lam Research Corp. COM 512807108 254 1,350 SH   SOLE   0 0 1,350
Lowes Cos Inc COM 548661107 320 3,174 SH   SOLE   0 0 3,174
Luminex Corp COM 55027E102 666 32,270 SH   SOLE   0 0 32,270
Mastercard Inc Cl A COM 57636q104 816 3,083 SH   SOLE   0 0 3,083
McCormick COM 579780206 17,369 112,050 SH   SOLE   0 0 112,050
McDermott Intl Inc COM 580037109 273 28,270 SH   SOLE   0 0 28,270
Medtronic PLC COM g5960l103 639 6,565 SH   SOLE   0 0 6,565
Merck & Co Inc New COM 58933Y105 202 2,411 SH   SOLE   0 0 2,411
Microsoft COM 594918104 50,312 375,576 SH   SOLE   0 0 375,576
National Instr COM 636518102 19,573 466,138 SH   SOLE   0 0 466,138
Netflix Inc COM 64110L106 588 1,600 SH   SOLE   0 0 1,600
Nokia COM 654902204 76 15,250 SH   SOLE   0 0 15,250
Nordson COM 655663102 36,439 257,863 SH   SOLE   0 0 257,863
Novartis AG COM 66987V109 18,194 199,258 SH   SOLE   0 0 199,258
Paccar COM 693718108 18,213 254,155 SH   SOLE   0 0 254,155
Paypal Hldgs Inc COM 70450Y103 375 3,280 SH   SOLE   0 0 3,280
PepsiCo COM 713448108 22,634 172,605 SH   SOLE   0 0 172,605
Phillips 66 COM COM 718546104 569 6,081 SH   SOLE   0 0 6,081
Procter & Gamble COM 742718109 23,487 214,197 SH   SOLE   0 0 214,197
Sabine Royalty Trust UBI COM 785688102 677 14,000 SH   SOLE   0 0 14,000
San Juan Basin Royalty Trust COM 798241105 2,480 647,452 SH   SOLE   0 0 647,452
Schlumberger Ltd COM 806857108 6,914 173,991 SH   SOLE   0 0 173,991
Sysco Corp COM 871829107 243 3,433 SH   SOLE   0 0 3,433
Taiwan Semiconductor COM 874039100 9,409 240,205 SH   SOLE   0 0 240,205
Telefonica de Espana COM 879382208 234 28,192 SH   SOLE   0 0 28,192
United Healthcare Corp COM 91324P102 416 1,705 SH   SOLE   0 0 1,705
United Parcel Svc Cl B COM 911312106 15,621 151,268 SH   SOLE   0 0 151,268
Walt Disney COM 254687106 312 2,236 SH   SOLE   0 0 2,236
Waste Management Inc Del COM 94106L109 404 3,500 SH   SOLE   0 0 3,500